Pub Date : 1990-09-01DOI: 10.1051/JPHYS:0199000510180202300
J. Friedel
Recent results on the cohesion of small neutral and ionised clusters of Na and K are interpreted in a simple Hubbard model, leading to values of transfer and Coulomb integrals of about 0.5 to 1 eV. These values justify the use of a Hartree Fock treatment of electron interactions and are coherent with the fairly compact structures of these aggregates Des resultats recents concernant la cohesion de petits amas neutres et ionises de Na et K sont interpretes dans un modele simple de Hubbard. Ils conduisent a des integrales de transfert et de Coulomb de l'ordre de 0,5 a 1 eV. Ces valeurs justifient l'utilisation d'un traitement de Hartree Fock des interactions electroniques et sont coherents avec les structures assez compactes de ces amas
{"title":"On the cohesion of small clusters of alkali metals","authors":"J. Friedel","doi":"10.1051/JPHYS:0199000510180202300","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510180202300","url":null,"abstract":"Recent results on the cohesion of small neutral and ionised clusters of Na and K are interpreted in a simple Hubbard model, leading to values of transfer and Coulomb integrals of about 0.5 to 1 eV. These values justify the use of a Hartree Fock treatment of electron interactions and are coherent with the fairly compact structures of these aggregates Des resultats recents concernant la cohesion de petits amas neutres et ionises de Na et K sont interpretes dans un modele simple de Hubbard. Ils conduisent a des integrales de transfert et de Coulomb de l'ordre de 0,5 a 1 eV. Ces valeurs justifient l'utilisation d'un traitement de Hartree Fock des interactions electroniques et sont coherents avec les structures assez compactes de ces amas","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"5 1","pages":"2023-2032"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87861336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-01DOI: 10.1051/JPHYS:0199000510180203300
J. Valognes, J. Bardet, C. Dimarcq, L. Giry
The time history of electronic density and temperature is a main point of the study of a resonantly laser created (weakly non-ideal) plasma. In order to carry out this study, with the aim of explaining the unusual variations of the emitted 4D→3P and 4F→3P Na(I) lines intensity, the authors perform a Star calculation (including ion-dynamic effect) and use as a diagnostic a comparison between experimental and theoretical profiles. Good agreement is obtained for most of the records. As for the Na 3P-level population, its time history is close to those already obtained in other studies, with different experimental conditions but for comparable densities L'evolution de la densite electronique et de la temperature est un point essentiel de l'etude d'un plasma (faiblement non ideal) obtenu par resonance laser. Afin d'effectuer cette etude, dans le but d'expliquer les variations inhabituelles observees, de l'intensite des raies 4D→3P et 4F→3P de Na(I), les auteurs utilisent un calcul de perturbation Stark (tenant en compte d'un effet dynamique des ions) et basent leur diagnostic sur la comparaison entre les profils experimentaux et theoriques. Un bon accord est obtenu dans la majorite des cas. Quand a la population du niveau 3P, son evolution est a rapprocher de celle deja mise en evidence par d'autres travaux, dans des conditions experimentales differentes mais pour des densites proches
电子密度和温度的时程是研究共振激光产生的(弱非理想)等离子体的一个重点。为了进行这项研究，以解释发射的4D→3P和4F→3P Na(I)线强度的不寻常变化为目的，作者进行了Star计算(包括离子动力学效应)，并将实验和理论资料之间的比较作为诊断。大多数记录的一致性很好。对于Na - 3p能级的居群，它的时间历史与其他研究中已经得到的时间历史接近，在不同的实验条件下，对于密度相当的L'evolution de la dense electronique和de la temperature est un point本质de L 'etude d'un plasma(失效非理想)obtenu par共振激光器。在d' efferette研究中，d' efferette研究中，d' explierle研究中，d' explierle研究中，d' intenterdes 4D→3P et 4F→3P de Na(I)， d' auteres利用计算摄动Stark (tenant en完成d' efferdynamicdes)，以及基本的lelediagnostic sur比较中心，实验和理论的轮廓。在多数情况下，碳协议是最容易达成的。从种群的角度来看，进化是细胞分化的一种途径，在不同的条件下，实验证明了不同的主要因素和密度途径
{"title":"Spectral diagnostic of a resonantly laser created non-Debye plasma","authors":"J. Valognes, J. Bardet, C. Dimarcq, L. Giry","doi":"10.1051/JPHYS:0199000510180203300","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510180203300","url":null,"abstract":"The time history of electronic density and temperature is a main point of the study of a resonantly laser created (weakly non-ideal) plasma. In order to carry out this study, with the aim of explaining the unusual variations of the emitted 4D→3P and 4F→3P Na(I) lines intensity, the authors perform a Star calculation (including ion-dynamic effect) and use as a diagnostic a comparison between experimental and theoretical profiles. Good agreement is obtained for most of the records. As for the Na 3P-level population, its time history is close to those already obtained in other studies, with different experimental conditions but for comparable densities L'evolution de la densite electronique et de la temperature est un point essentiel de l'etude d'un plasma (faiblement non ideal) obtenu par resonance laser. Afin d'effectuer cette etude, dans le but d'expliquer les variations inhabituelles observees, de l'intensite des raies 4D→3P et 4F→3P de Na(I), les auteurs utilisent un calcul de perturbation Stark (tenant en compte d'un effet dynamique des ions) et basent leur diagnostic sur la comparaison entre les profils experimentaux et theoriques. Un bon accord est obtenu dans la majorite des cas. Quand a la population du niveau 3P, son evolution est a rapprocher de celle deja mise en evidence par d'autres travaux, dans des conditions experimentales differentes mais pour des densites proches","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"1 1","pages":"2033-2049"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90412515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-01DOI: 10.1051/JPHYS:0199000510180201500
M. Zgonik, M. Rey-Lafon, C. Destrade, C. Leon, H. Nguyen
Orientationa order in smectic phases of a ferroelectric liquid-crystalline material 4'-(2S,3S)-2″-chloro-3″-methylpentanoyloxyphenyl-4-decyloxy thiobenzoate, abbreviated 10.S.C1Isolleu, was examined by IR absorption spectroscopy. Oriented samples were prepared in both bookshelf and homeotropic alignment geometry. Several stronger IR vibrations were selected characterizing different parts and orientations of the molecules. Results show that the molecular tilt of the core parts of the molecules changes very little from the S A to the S C * phase implying that the core parts of the molecules are already tilted in the S A phase. Axes of the core parts, that are disordered on a cone in the S A phase, start to align with each other but remain on this cone on lowering the temperature into the S C * phase. The model agrees with some previous results On a etudie par spectroscopie d'absorption infrarouge l'ordre orientationnel dans les phases smectiques d'un materiau cristal liquide ferroelectrique, le decyloxy-4-thiobenzoate de [(2S,3S)-chloro-2-methyl-3-pentanoyloxy]-4'-phenyle, en abrege 10.S.C1Isoleu. Deux types d'echantillons orientes, l'un homeotrope, l'autre en configuration Clark-Lagerwall, ont ete prepares et plusieurs bandes intenses en infrarouge, caracteristiques des differentes parties et orientations des molecules, ont ete choisies. Les resultats montrent que l'inclinaison des parties centrales (cœurs) des molecules varie tres peu de la phase S A a la phase S C *, ce qui implique que les cœurs des molecules sont deja inclines dans la phase S A . Leurs axes, qui sont desordonnes sur un cone dans la phase S A , s'alignent mais restent sur ce cone quand on passe en phase S C * en abaissant la temperature. Ce modele est en accord avec quelques resultats anterieurs
铁电液晶材料4′-(2S,3S)-2″-氯-3″-甲基戊氧基苯基-4-癸氧基硫苯甲酸酯(简称10.S)的取向顺序用红外吸收光谱法对C1Isolleu进行了表征。在书架和各向同性排列几何中制备了定向样品。选择了几种较强的红外振动来表征分子的不同部分和方向。结果表明，从sa相到sc *相，分子核心部分的分子倾斜度变化很小，表明分子核心部分在sa相已经倾斜。核心部分的轴线在sa相的锥体上无序，开始彼此对齐，但在降低温度进入sc *相时仍保持在该锥体上。该模型与先前的一些研究结果相一致，这些结果是通过对材料晶体液体铁电体，四烷基氧基-4-硫苯酸盐[(2S,3S)-氯-2-甲基-3-戊氧基]-4'-苯基的光谱分析得出的。两种类型的力学取向，一种类型的同向异性，一种类型的构型，一种类型的克拉克-拉格沃尔，一种类型的制备，一种类型的多波段强度，一种类型的特征，一种类型的分子取向，一种类型的选择。Les results montrent que l' ininaison des parties centrales (cœurs) des molecules varies peu de la phase sa A la phase sc *， ce qui implque Les cœurs des molecules sonja injines dans la phase sa。在温度恒定的情况下，低轴、低轴、低轴、低轴、低轴、低轴、低轴、低轴、低轴、低轴、低轴、低轴、低轴、低轴。该模型的测试结果与实验结果一致
{"title":"Microscopic ordering in smectic phases of liquid crystals","authors":"M. Zgonik, M. Rey-Lafon, C. Destrade, C. Leon, H. Nguyen","doi":"10.1051/JPHYS:0199000510180201500","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510180201500","url":null,"abstract":"Orientationa order in smectic phases of a ferroelectric liquid-crystalline material 4'-(2S,3S)-2″-chloro-3″-methylpentanoyloxyphenyl-4-decyloxy thiobenzoate, abbreviated 10.S.C1Isolleu, was examined by IR absorption spectroscopy. Oriented samples were prepared in both bookshelf and homeotropic alignment geometry. Several stronger IR vibrations were selected characterizing different parts and orientations of the molecules. Results show that the molecular tilt of the core parts of the molecules changes very little from the S A to the S C * phase implying that the core parts of the molecules are already tilted in the S A phase. Axes of the core parts, that are disordered on a cone in the S A phase, start to align with each other but remain on this cone on lowering the temperature into the S C * phase. The model agrees with some previous results On a etudie par spectroscopie d'absorption infrarouge l'ordre orientationnel dans les phases smectiques d'un materiau cristal liquide ferroelectrique, le decyloxy-4-thiobenzoate de [(2S,3S)-chloro-2-methyl-3-pentanoyloxy]-4'-phenyle, en abrege 10.S.C1Isoleu. Deux types d'echantillons orientes, l'un homeotrope, l'autre en configuration Clark-Lagerwall, ont ete prepares et plusieurs bandes intenses en infrarouge, caracteristiques des differentes parties et orientations des molecules, ont ete choisies. Les resultats montrent que l'inclinaison des parties centrales (cœurs) des molecules varie tres peu de la phase S A a la phase S C *, ce qui implique que les cœurs des molecules sont deja inclines dans la phase S A . Leurs axes, qui sont desordonnes sur un cone dans la phase S A , s'alignent mais restent sur ce cone quand on passe en phase S C * en abaissant la temperature. Ce modele est en accord avec quelques resultats anterieurs","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"29 1","pages":"2015-2022"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81413235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-01DOI: 10.1051/JPHYS:0199000510170178500
M. Quilichini, G. Heger, B. Hennion, S. Lefébvre, A. Quivy
Inelastic neutron scattering results evidenced for the first time that acoustic phonon modes can be observed for a quasicrystal. The triple-axes experiments have been performed on a small monodomain Al63Cu 25Fe12 sample. The obtained TA and LA dispersion curves near to strong Bragg peaks do not show any variation with respect to different Q values. Their slopes are isotropic and do not depend on special symmetry directions; they are comparable to those of corresponding curves for pure aluminium. We have not been able to observe energy gaps in our measurements.
{"title":"Inelastic neutron scattering study of acoustic modes in a monodomain AlCuFe quasicrystal","authors":"M. Quilichini, G. Heger, B. Hennion, S. Lefébvre, A. Quivy","doi":"10.1051/JPHYS:0199000510170178500","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510170178500","url":null,"abstract":"Inelastic neutron scattering results evidenced for the first time that acoustic phonon modes can be observed for a quasicrystal. The triple-axes experiments have been performed on a small monodomain Al63Cu 25Fe12 sample. The obtained TA and LA dispersion curves near to strong Bragg peaks do not show any variation with respect to different Q values. Their slopes are isotropic and do not depend on special symmetry directions; they are comparable to those of corresponding curves for pure aluminium. We have not been able to observe energy gaps in our measurements.","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"51 1","pages":"1785-1790"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85468911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-01DOI: 10.1051/JPHYS:0199000510170186500
B. Caroli, C. Caroli, B. Roulet
We analyze the linear stability of the periodic eutectic lamellar patterns studied in the preceding article [I] with respect to long wavelength perturbations. We show that, in the large thermal gradient limit considered in [I], and for patterns with wavelengths comparable with the minimum undercooling one, λ min : 1) an instability with respect to a quasi-uniform variation of the phase fraction occurs only for mixtures with a departure from eutectic composition u∞ on the side of the phase diagram with the larger liquid-solid temperature gap. In this case, stationary patterns with λ Nous analysons la stabilite lineaire des structures eutectiques lamellaires periodiques stationnaires etudiees dans l'article precedent [I] vis-a-vis des perturbations de grande longueur d'onde. Nous montrons que, dans la limite des grands gradients thermiques consideree dans [I], et pour les structures de longueur d'onde de l'ordre de celle, λ min , correspondant au surrefroidissement minimum: 1) il apparait une instabilite associee a une variation quasi uniforme de la proportion de chacune des deux phases solides. Elle apparait seulement pour les melanges dont l'ecart u∞, a la composition eutectique est du cote du diagramme de phase qui presente le plus grand «gap» de temperature. Dans ce cas, les structures stationnaires avec λ<λ 0 , ou λ 0 αu ∞ , sont instables; 2) toutes les structures avec λ/λ min =0 (1) sont stables vis-a-vis du mecanisme d'Eckhaus. Ceci entraine que l'hypothese dynamique utilisee dans des travaux anterieurs, selon laquelle les interfaces solide-solide seraient localement normales au front, n'est pas compatible avec l'approximation usuelle des petites deformations de front
我们分析了上一篇文章[1]中所研究的周期共晶片层图在长波摄动下的线性稳定性。我们表明，在[I]中考虑的大热梯度极限下，对于波长与最小过冷模式相当的模式，λ min: 1)相对于准均匀变化的相分数的不稳定性只发生在相图中液固温差较大的一侧偏离共晶成分u∞的混合物中。在这种情况下，具有λ Nous分析的平稳模式la stabilite lineaire des structures eutectiques lamellaires periodicaldiques stationures studes and l'article precedent[1]相对于de grande longueur d'onde的扰动。Nous montrons que, dans la限制des grand gradients ides dans [I]， et pour les structures de longueur d'onde de l'ordre de celle， λ min，对应于表面冷冻最小值:1)将出现一个不稳定的结合体和一个变化准均匀的de la比例de chacune de双相固体。Elle appartseulement pour les melanges don 'ecart u∞，a la composition eutectique est du cote du diagram de phase ques present le + grand“gap”de temperature。随着时间的增加，结构站的平均λ<λ 0， λ 0 αu∞，不稳定;(2)构造平均λ/λ min =0(1)稳态相对于埃克豪斯力学。塞西·特伦纳克(Ceci entraine quel’假设)的动力学利用，采用了前体变形法;塞西·特伦纳克(selon laquelle)采用了前体变形法;塞西·特伦纳克(selon laquelle)采用了前体变形法
{"title":"Lamellar eutectic growth at large thermal gradient. II. Linear stability","authors":"B. Caroli, C. Caroli, B. Roulet","doi":"10.1051/JPHYS:0199000510170186500","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510170186500","url":null,"abstract":"We analyze the linear stability of the periodic eutectic lamellar patterns studied in the preceding article [I] with respect to long wavelength perturbations. We show that, in the large thermal gradient limit considered in [I], and for patterns with wavelengths comparable with the minimum undercooling one, λ min : 1) an instability with respect to a quasi-uniform variation of the phase fraction occurs only for mixtures with a departure from eutectic composition u∞ on the side of the phase diagram with the larger liquid-solid temperature gap. In this case, stationary patterns with λ Nous analysons la stabilite lineaire des structures eutectiques lamellaires periodiques stationnaires etudiees dans l'article precedent [I] vis-a-vis des perturbations de grande longueur d'onde. Nous montrons que, dans la limite des grands gradients thermiques consideree dans [I], et pour les structures de longueur d'onde de l'ordre de celle, λ min , correspondant au surrefroidissement minimum: 1) il apparait une instabilite associee a une variation quasi uniforme de la proportion de chacune des deux phases solides. Elle apparait seulement pour les melanges dont l'ecart u∞, a la composition eutectique est du cote du diagramme de phase qui presente le plus grand «gap» de temperature. Dans ce cas, les structures stationnaires avec λ<λ 0 , ou λ 0 αu ∞ , sont instables; 2) toutes les structures avec λ/λ min =0 (1) sont stables vis-a-vis du mecanisme d'Eckhaus. Ceci entraine que l'hypothese dynamique utilisee dans des travaux anterieurs, selon laquelle les interfaces solide-solide seraient localement normales au front, n'est pas compatible avec l'approximation usuelle des petites deformations de front","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"63 1","pages":"1865-1876"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85473923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-01DOI: 10.1051/JPHYS:0199000510180200500
B. Piveteau, C. Noguera
Associating for the first time a total energy calculation and a phase transition approach, we present an analysis of the relative stability of two structural phases in an ionic compound at zero temperature. This new combination of two classical methods allows a progressive discovery of the microscopic relevant interactions associated with each distortion, and yields the value of the Landau coefficients in the development of the energy. Illustrated on the compound La 2 CuO 4 , this method has a wide applicability in the field of the structural stability of ionic systems En associant, pour la premiere fois, un calcul d'energie de cohesion et une approche a la Landau des transitions de phase, nous presentons une analyse de la stabilite relative de deux phases structurales d'un compose ionique a 0 K. Cette association de deux methodes, en elles memes classiques, permet de decouvrir progressivement les interactions microscopiques associees a chaque distortion, et fournit les valeurs numeriques des coefficients de Landau dans le developpement d'energie correspondant. Cette methode illustree ici sur le compose La 2 CuO 4 ouvre un large champ d'investigation dans le domaine des stabilites structurales des composes ioniques
{"title":"Microscopic analysis of structure stabilities in the ionic compounds","authors":"B. Piveteau, C. Noguera","doi":"10.1051/JPHYS:0199000510180200500","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510180200500","url":null,"abstract":"Associating for the first time a total energy calculation and a phase transition approach, we present an analysis of the relative stability of two structural phases in an ionic compound at zero temperature. This new combination of two classical methods allows a progressive discovery of the microscopic relevant interactions associated with each distortion, and yields the value of the Landau coefficients in the development of the energy. Illustrated on the compound La 2 CuO 4 , this method has a wide applicability in the field of the structural stability of ionic systems En associant, pour la premiere fois, un calcul d'energie de cohesion et une approche a la Landau des transitions de phase, nous presentons une analyse de la stabilite relative de deux phases structurales d'un compose ionique a 0 K. Cette association de deux methodes, en elles memes classiques, permet de decouvrir progressivement les interactions microscopiques associees a chaque distortion, et fournit les valeurs numeriques des coefficients de Landau dans le developpement d'energie correspondant. Cette methode illustree ici sur le compose La 2 CuO 4 ouvre un large champ d'investigation dans le domaine des stabilites structurales des composes ioniques","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"40 1","pages":"2005-2010"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85080833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-01DOI: 10.1051/JPHYS:0199000510180208700
H. Kitzerow, G. Heppke, H. Schmid, B. Jérôme, P. Pieranski
By means of optical microscopy, Kossel diagrams of chiral smectic phases are observed for the dirst time. Due to Bragg reflection, these diagrams occur in the focal plane of the microscope lens if the sample is illuminated with convergent monochromatic light. The Kossel diagram for the SmC* phase ― observed for the chiral compound CE3 (BDH) ― consists of a central ring corresponding to the periodicity p/2 of the |m|=2 mode of the tensor order parameter e(r) describing the helical structure. The temperature dependence of the pitch p(T) determined by the Kossel method is in agreement with spectroscopic investigations of the Bragg scattering in back reflection. The Kossel diagrams of the unknown chiral smectic structure SmM* consist also of one central ring; no additional reciprocal lattice vectors are observed in the visible wavelength range for this phase. In addition to the Kossel diagrams, we report on the observation of Airy spirals in the SmC* phase Au moyen d'un microscope polarisant en configuration conoscopique on etudie pour la premiere fois les diagrammes de Kossel des phases chirales SmC* et SmM*. Dans le cas de la phase SmC* on observe un seul anneau de Kossel correspondant a la periodicite p/2 de la composante tensorielle |m|=2 de la structure helicoidale du parametre d'ordre e(r). La variation du pas p(T) en fonction de la temperature, obtenue a partir des diagrammes de Kossel, est en accord avec des mesures faites independamment par reflexion de Bragg en incidence normale aux couches smectiques. Le diagramme de Kossel de la phase SmM* comporte aussi un seul anneau central. En plus d'anneau de Kossel, dans le cas de la phase SmC* on observe des spirales d'Airy
利用光学显微镜首次观察到手性晶相的科塞尔图。由于布拉格反射，如果样品用会聚单色光照射，这些图就会出现在显微镜透镜的焦平面上。手性化合物CE3 (BDH)的SmC*相的Kossel图由一个中心环组成，该中心环对应于描述螺旋结构的张量阶参数e(r)的|m|=2模式的周期性p/2。由科塞尔方法确定的节距p(T)的温度依赖性与背反射布拉格散射的光谱研究一致。未知手性微晶结构SmM*的科塞尔图也由一个中心环组成;在该相位的可见波长范围内没有观察到额外的互易晶格矢量。除了科塞尔图外，我们还报道了用光学显微镜观察到的SmC*相中的Airy螺旋现象。Dans le cas de la相SmC* on on observe unseul anneau de Kossel对应于la periodicite p/2 de la composante tensorielle |m|=2 de la structure helicoidale du parameter d' order e(r)。p(T)随温度的变化，得到了科塞尔图的一部分，测试了测量值的独立性与反射的Bragg入射法线的关系。Le diagramme de Kossel de la phase SmM* comcomte aussi un seul anneau central。En + d'anneau de Kossel，在观察airy的螺旋上，研究了相位SmC*的结构
{"title":"First optical observation of Kossel diagrams in chiral smectic phases","authors":"H. Kitzerow, G. Heppke, H. Schmid, B. Jérôme, P. Pieranski","doi":"10.1051/JPHYS:0199000510180208700","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510180208700","url":null,"abstract":"By means of optical microscopy, Kossel diagrams of chiral smectic phases are observed for the dirst time. Due to Bragg reflection, these diagrams occur in the focal plane of the microscope lens if the sample is illuminated with convergent monochromatic light. The Kossel diagram for the SmC* phase ― observed for the chiral compound CE3 (BDH) ― consists of a central ring corresponding to the periodicity p/2 of the |m|=2 mode of the tensor order parameter e(r) describing the helical structure. The temperature dependence of the pitch p(T) determined by the Kossel method is in agreement with spectroscopic investigations of the Bragg scattering in back reflection. The Kossel diagrams of the unknown chiral smectic structure SmM* consist also of one central ring; no additional reciprocal lattice vectors are observed in the visible wavelength range for this phase. In addition to the Kossel diagrams, we report on the observation of Airy spirals in the SmC* phase Au moyen d'un microscope polarisant en configuration conoscopique on etudie pour la premiere fois les diagrammes de Kossel des phases chirales SmC* et SmM*. Dans le cas de la phase SmC* on observe un seul anneau de Kossel correspondant a la periodicite p/2 de la composante tensorielle |m|=2 de la structure helicoidale du parametre d'ordre e(r). La variation du pas p(T) en fonction de la temperature, obtenue a partir des diagrammes de Kossel, est en accord avec des mesures faites independamment par reflexion de Bragg en incidence normale aux couches smectiques. Le diagramme de Kossel de la phase SmM* comporte aussi un seul anneau central. En plus d'anneau de Kossel, dans le cas de la phase SmC* on observe des spirales d'Airy","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"171 1","pages":"2087-2099"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83372655","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-01DOI: 10.1051/JPHYS:0199000510170180300
R. Rammal, J. Bellissard
Starting from Heisenberg's point of view, a semi-classical quantization method is introduced for 2D Bloch electrons in a magnetic field. The underlying lattice structure is used to define an algebraic structure. The (rotation) algebra so defined is non commutative, but allows for a systematic expansion of the magnetic energy levels, free energy, etc. near zero as well as an arbitrary rational flux. All previously derived results are recovered as special cases, but without involving wave function considerations (WKB, equation-of-motion methods, etc.). New results, up to second order in the magnetic flux, are explicity derived and simple examples are used to illustrate our general algebraic formalism En adoptant le point de vue de Heisenberg, on introduit une nouvelle methode de quantification semi-classique, pour les electrons de Bloch sous champ magnetique. La structure du reseau est utilisee pour definir une structure algebrique. L'algebre, dite de rotation, ainsi definie est non commutative, mais permet d'avoir un developpement systematique a flux nul ainsi qu'a flux rationnel quelconque. L'ensemble des resultats connus sont retrouves dans le cadre de notre formalisme, sans faire appel a la notion de fonction d'onde telle que dans la methode WKB ou celle de l'equation du mouvement par exemple. Des nouveaux resultats, jusqu'au second ordre en flux sont donnes ainsi que des exemples simples pour illustrer la methode algebrique
从海森堡的观点出发，介绍了二维布洛赫电子在磁场中的半经典量子化方法。底层的点阵结构用于定义代数结构。这样定义的(旋转)代数是不可交换的，但允许磁能水平、自由能等在零附近的系统扩展，以及任意有理通量。所有先前导出的结果都是作为特殊情况恢复的，但不涉及波函数的考虑(WKB，运动方程方法等)。新的结果，直到磁通量的二阶，是显式推导和简单的例子，说明我们的一般代数形式En采用le point de vue de Heisenberg，在引入一个新的方法的量化半经典，pour les电子de Bloch sous champ磁。研究的结构是用来定义一个结构代数的。代数，除了旋转之外，它定义了非交换性，主要是允许在发展系统中使用通量，而不是通量，而不是通量。L 'ensemble结果有名在干部中retrouves formalisme德诺特,无做appel de概念以d 'onde在某个方法WKB ou celle de等式du比如所属。新结果、新方法、新结果、新结果、新结果、新结果、新结果、新结果、新结果、新结果、新结果、新结果、新结果
{"title":"An algebraic semi-classical approach to Bloch electrons in a magnetic field","authors":"R. Rammal, J. Bellissard","doi":"10.1051/JPHYS:0199000510170180300","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510170180300","url":null,"abstract":"Starting from Heisenberg's point of view, a semi-classical quantization method is introduced for 2D Bloch electrons in a magnetic field. The underlying lattice structure is used to define an algebraic structure. The (rotation) algebra so defined is non commutative, but allows for a systematic expansion of the magnetic energy levels, free energy, etc. near zero as well as an arbitrary rational flux. All previously derived results are recovered as special cases, but without involving wave function considerations (WKB, equation-of-motion methods, etc.). New results, up to second order in the magnetic flux, are explicity derived and simple examples are used to illustrate our general algebraic formalism En adoptant le point de vue de Heisenberg, on introduit une nouvelle methode de quantification semi-classique, pour les electrons de Bloch sous champ magnetique. La structure du reseau est utilisee pour definir une structure algebrique. L'algebre, dite de rotation, ainsi definie est non commutative, mais permet d'avoir un developpement systematique a flux nul ainsi qu'a flux rationnel quelconque. L'ensemble des resultats connus sont retrouves dans le cadre de notre formalisme, sans faire appel a la notion de fonction d'onde telle que dans la methode WKB ou celle de l'equation du mouvement par exemple. Des nouveaux resultats, jusqu'au second ordre en flux sont donnes ainsi que des exemples simples pour illustrer la methode algebrique","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"12 1","pages":"1803-1830"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84083052","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-01DOI: 10.1051/JPHYS:0199000510170184700
K. Brattkus, B. Caroli, C. Caroli, B. Roulet
We study stationary front profiles of directionally solidified lamellar eutectics. We show that, in the limit of large thermal gradients, front shapes can be calculated analytically without resorting to the Jackson-Hunt ansatz [7] of equal average front undercooling of both phases. We find that the difference between them is comparable with the global average one ΔT, but that the variation of ΔT with the lamellar period λ exhibits a minimum for a value of λ of the same order of magnitude as that predicted by J. H. We look for stationary tilted solutions. These can occur in general for isolated values of the tilt angle, but are absent in the large gradient limit, in agreement with the experimental observation of a velocity threshold for «tilt waves» Nous etudions les profils de fronts stationnaires des eutectiques lamellaires en solidification directionnelle. Nous montrons que, dans la limite des grands gradients thermiques, on peut calculer analytiquement ces formes de front sans avoir recours a l'hypothese d'egalite des surrefroidissements de front moyens des deux phases faite par Jackson et Hunt [7]. Nous trouvons que la difference entre ces quantites est comparable au surrefroidissement moyen global ΔT, mais que ΔT presente au minimum a une valeur de la longueur d'onde lamellaire du meme ordre de grandeur que celle predite par J.H. Nous cherchons s'il existe des solutions a lamelles inclinees, et montrons qu'elles ne peuvent, en general, exister que pour des valeurs isolees de l'angle d'inclinaison, mais qu'elles sont absentes a grand gradient, en accord avec l'observation experimentale d'un seuil de vitesse pour les «ondes d'inclinaison»
本文研究了定向凝固层状共晶的静止前沿轮廓。我们证明，在大热梯度的限制下，可以解析地计算锋面形状，而不需要借助于两相平均锋面过冷相等的Jackson-Hunt分析[7]。我们发现它们之间的差异与全球平均值ΔT相当，但是，ΔT与片层周期λ的变化表现出与J. H.预测的相同数量级的λ值的最小值。这些通常可以在倾斜角度的孤立值中发生，但在大梯度极限中不存在，这与“倾斜波”的速度阈值的实验观察相一致，这与Nous etutuons les profiles de frontiques des eutectiques lamellaires en凝固方向一致。Nous montrons que, dans la limite des grand gradients thermomiques，在计算机分析上，在没有avoir recours的情况下形成了一个“假设”(假设)，在两相的情况下形成了一个“假设”(假设)，如Jackson和Hunt[7]。常识trouvons ces数量之间差异是可比的非盟surrefroidissement平均全球ΔT,但是ΔT现在盟最低一个一个的数值de la小说d 'onde lamellaire du meme范围富丽堂皇,celle predite par J.H.常识cherchons年代有des的解决方案中存在一个lamelles斜坡,et montrons相关peuvent,一般来说,存在的百分比值隔离de l 'angle d 'inclinaison,但是它们是缺席一场盛大的梯度,根据《观察与实验》，《联合国的观察与实验》为《倾向与实验》提供了依据
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Pub Date : 1990-09-01DOI: 10.1051/JPHYS:0199000510180207300
A. Poquérusse
{"title":"Recombinaison radiative directe le long de plusieurs séquences isoélectroniques","authors":"A. Poquérusse","doi":"10.1051/JPHYS:0199000510180207300","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510180207300","url":null,"abstract":"","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"200 1","pages":"2073-2085"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74531174","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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