Pub Date : 1967-12-01DOI: 10.1088/0508-3443/18/12/307
D. J. Saunders, K. Standley, P. G. Wilson
Ruby samples manufactured by three different techniques were used in electron paramagnetic resonance studies at 35 and 115 GHz, at room temperature and 77°k. In contrast with the spin-lattice relaxation results of Standley and Vaughan, no significant differences were observed between vapour-phase, Verneuil or fluxedmelt samples in relation to zero-field splitting of the energy levels, linewidths, intensities of Cr-Cr pair lines or impurity spectra. Data on these parameters are given. Evidence is presented of a variation in zero-field splitting of approximately 10% in one sample, leading to a greatly increased linewidth of some transitions.
{"title":"Microwave resonance absorption in ruby","authors":"D. J. Saunders, K. Standley, P. G. Wilson","doi":"10.1088/0508-3443/18/12/307","DOIUrl":"https://doi.org/10.1088/0508-3443/18/12/307","url":null,"abstract":"Ruby samples manufactured by three different techniques were used in electron paramagnetic resonance studies at 35 and 115 GHz, at room temperature and 77°k. In contrast with the spin-lattice relaxation results of Standley and Vaughan, no significant differences were observed between vapour-phase, Verneuil or fluxedmelt samples in relation to zero-field splitting of the energy levels, linewidths, intensities of Cr-Cr pair lines or impurity spectra. Data on these parameters are given. Evidence is presented of a variation in zero-field splitting of approximately 10% in one sample, leading to a greatly increased linewidth of some transitions.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"222 1","pages":"1723-1729"},"PeriodicalIF":0.0,"publicationDate":"1967-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73011208","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 : 1967-12-01DOI: 10.1088/0508-3443/18/12/313
R. Gambhir
Theory of Saxena, Saksena and Gambhir has been extended to include polyatomic gases having more than one relaxation time. The results have been compared with experiment for CO2 and N2O. Theories of Monchick, Pereira and Mason, Hirschfelder, and others have also been considered. In the case of CO2 all theories fit equally well with experiment while for N2O the expression given in this paper is preferable.
{"title":"Heat conduction through CO2 and N2O gases","authors":"R. Gambhir","doi":"10.1088/0508-3443/18/12/313","DOIUrl":"https://doi.org/10.1088/0508-3443/18/12/313","url":null,"abstract":"Theory of Saxena, Saksena and Gambhir has been extended to include polyatomic gases having more than one relaxation time. The results have been compared with experiment for CO2 and N2O. Theories of Monchick, Pereira and Mason, Hirschfelder, and others have also been considered. In the case of CO2 all theories fit equally well with experiment while for N2O the expression given in this paper is preferable.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"202 1","pages":"1773-1775"},"PeriodicalIF":0.0,"publicationDate":"1967-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86835893","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 : 1967-12-01DOI: 10.1088/0508-3443/18/12/311
D. Bassett
Field desorption of oxygen from initially field-evaporated tungsten surfaces has been investigated to determine the extent to which the adsorbate is retained on the surface under the conditions for imaging in a field-ion microscope. Desorption of oxygen occurs in vacuum for electric fields greater than half the field needed to evaporate the tungsten substrate, probably by the desorption of oxide ions. Desorption occurs to only limited extent at a particular field because the energy barrier to desorption rises as desorption proceeds. The extent of desorption is greater the higher the electric field, and at the helium imaging field little adsorbate is retained on the surface. Desorption is greatly enhanced by the presence of the inert gases used in imaging. Helium, neon and argon at 1 mtorr lower the field for desorption to a particular oxygen coverage by approximately 12, 17 and 32% respectively. Differences between the character of desorption in vacuum and in gas and estimates of the height of the energy barriers to desorption in gas strongly suggest that the enhancement of desorption is caused primarily by energetic electrons released by field ionization of the inert gas. The extent of desorption in helium and neon at 78?K indicates that very little, if any, adsorbed oxygen is retained on a tungsten surface for the periods required in recording ion micrographs without image amplification.
{"title":"The enhancement by inert gases of the field desorption of oxygen from tungsten","authors":"D. Bassett","doi":"10.1088/0508-3443/18/12/311","DOIUrl":"https://doi.org/10.1088/0508-3443/18/12/311","url":null,"abstract":"Field desorption of oxygen from initially field-evaporated tungsten surfaces has been investigated to determine the extent to which the adsorbate is retained on the surface under the conditions for imaging in a field-ion microscope. Desorption of oxygen occurs in vacuum for electric fields greater than half the field needed to evaporate the tungsten substrate, probably by the desorption of oxide ions. Desorption occurs to only limited extent at a particular field because the energy barrier to desorption rises as desorption proceeds. The extent of desorption is greater the higher the electric field, and at the helium imaging field little adsorbate is retained on the surface. Desorption is greatly enhanced by the presence of the inert gases used in imaging. Helium, neon and argon at 1 mtorr lower the field for desorption to a particular oxygen coverage by approximately 12, 17 and 32% respectively. Differences between the character of desorption in vacuum and in gas and estimates of the height of the energy barriers to desorption in gas strongly suggest that the enhancement of desorption is caused primarily by energetic electrons released by field ionization of the inert gas. The extent of desorption in helium and neon at 78?K indicates that very little, if any, adsorbed oxygen is retained on a tungsten surface for the periods required in recording ion micrographs without image amplification.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"8 1","pages":"1753-1761"},"PeriodicalIF":0.0,"publicationDate":"1967-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87877482","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 : 1967-12-01DOI: 10.1088/0508-3443/18/12/128
C. Deenadas, H. Keer, R. V. Gopalarao, A. Biswas
The heat capacity of potassium cobalt trifluoride was recorded over the range 80-300°K. A peak at 1095°K is attributed to an antiferromagnetic-paramagnetic transition. The values of heat capacity, entropy, enthalpy and free energy at 29815°K are 2884 cal mole-1 degK-1, 3940 cal mole-1 degK-1, 5669 cal mole-1 and - 2026 cal mole-1 degK-1, respectively.
记录了三氟化钴钾在80-300°K范围内的热容。1095°K处的峰值归因于反铁磁-顺磁跃迁。29815°K时的热容、熵、焓和自由能分别为2884 cal mol -1 degK-1、3940 cal mol -1 degK-1、5669 cal mol -1和- 2026 cal mol -1 degK-1。
{"title":"Heat capacity of potassium cobalt trifluoride","authors":"C. Deenadas, H. Keer, R. V. Gopalarao, A. Biswas","doi":"10.1088/0508-3443/18/12/128","DOIUrl":"https://doi.org/10.1088/0508-3443/18/12/128","url":null,"abstract":"The heat capacity of potassium cobalt trifluoride was recorded over the range 80-300°K. A peak at 1095°K is attributed to an antiferromagnetic-paramagnetic transition. The values of heat capacity, entropy, enthalpy and free energy at 29815°K are 2884 cal mole-1 degK-1, 3940 cal mole-1 degK-1, 5669 cal mole-1 and - 2026 cal mole-1 degK-1, respectively.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"62 1","pages":"1833-1834"},"PeriodicalIF":0.0,"publicationDate":"1967-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83942651","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 : 1967-12-01DOI: 10.1088/0508-3443/18/12/320
J. Kramer
The potential in a cylindrical arrangement of electrodes or coils is described by means of Fourier series of which the first harmonic supplies the homogeneous field. From the development the influence of higher harmonics can easily be seen. As an example this treatment is applied to the construction of two simple systems in which several higher harmonics are eliminated. To demonstrate this elimination both systems were used as deflectors in an electron-optical set-up.
{"title":"Production of homogeneous fields","authors":"J. Kramer","doi":"10.1088/0508-3443/18/12/320","DOIUrl":"https://doi.org/10.1088/0508-3443/18/12/320","url":null,"abstract":"The potential in a cylindrical arrangement of electrodes or coils is described by means of Fourier series of which the first harmonic supplies the homogeneous field. From the development the influence of higher harmonics can easily be seen. As an example this treatment is applied to the construction of two simple systems in which several higher harmonics are eliminated. To demonstrate this elimination both systems were used as deflectors in an electron-optical set-up.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"3 1","pages":"1815-1818"},"PeriodicalIF":0.0,"publicationDate":"1967-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85416843","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 : 1967-12-01DOI: 10.1088/0508-3443/18/12/302
W. Price
A new mechanical action method for the determination of the principal dielectric constants of synthetic sapphire is described. It is based on measurements of the couple experienced by a sphere of the material suspended in a uniform electric field. The values were found to be [perpendicular] = 79 ± 05 and [parallel] = 65 ± 04 when measured at a frequency of 50 Hz, and these values compare favourably with those obtained by other methods. The method may be applied to anisotropic crystals in general, and it is suggested that with slight modification it may be used for the corresponding electrical conductivity determinations.
{"title":"The measurement of the principal dielectric constants of sapphire by a mechanical action method","authors":"W. Price","doi":"10.1088/0508-3443/18/12/302","DOIUrl":"https://doi.org/10.1088/0508-3443/18/12/302","url":null,"abstract":"A new mechanical action method for the determination of the principal dielectric constants of synthetic sapphire is described. It is based on measurements of the couple experienced by a sphere of the material suspended in a uniform electric field. The values were found to be [perpendicular] = 79 ± 05 and [parallel] = 65 ± 04 when measured at a frequency of 50 Hz, and these values compare favourably with those obtained by other methods. The method may be applied to anisotropic crystals in general, and it is suggested that with slight modification it may be used for the corresponding electrical conductivity determinations.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"1 1","pages":"1679-1688"},"PeriodicalIF":0.0,"publicationDate":"1967-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76201787","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 : 1967-12-01DOI: 10.1088/0508-3443/18/12/303
C. Miller
A qualitative description is presented for the behaviour of the hysteresis loss and the dielectric constant in ceramic barium titanate in terms of the properties of single-crystal barium titanate. When the effects of imperfections and interaction between crystallites are introduced, this description explains the similarity between the dielectric constants of single crystal and ceramic when the hysteresis losses differ by orders of magnitude. Measurements of the dependence of loss and dielectric constant on grain size, as a function of temperature, are described, and the results interpreted. A new explanation of the anomalously high dielectric constant of very fine-grain ceramic barium titanate is given.
{"title":"Hysteresis loss and dielectric constant in barium titanate","authors":"C. Miller","doi":"10.1088/0508-3443/18/12/303","DOIUrl":"https://doi.org/10.1088/0508-3443/18/12/303","url":null,"abstract":"A qualitative description is presented for the behaviour of the hysteresis loss and the dielectric constant in ceramic barium titanate in terms of the properties of single-crystal barium titanate. When the effects of imperfections and interaction between crystallites are introduced, this description explains the similarity between the dielectric constants of single crystal and ceramic when the hysteresis losses differ by orders of magnitude. Measurements of the dependence of loss and dielectric constant on grain size, as a function of temperature, are described, and the results interpreted. A new explanation of the anomalously high dielectric constant of very fine-grain ceramic barium titanate is given.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"296 1","pages":"1689-1697"},"PeriodicalIF":0.0,"publicationDate":"1967-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76471661","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 : 1967-12-01DOI: 10.1088/0508-3443/18/12/312
R. Lawson
A theory has been developed to account quantitatively for the anomalous ion-current behaviour which leads to errors in pressure measurement in Bayard-Alpert ionization gauges. The equilibrium anomalous ion current has been studied as a function of the gauge electron current and operating pressure. Analysis of the experimental results in the light of the theory yields values for the total atom and ion desorption probability per electron, the ion desorption probability per electron and the sticking coefficient of gas molecules on the grid surface. Though the theory suggests ways in which the pressure measurement error can be minimized, experiment shows that the error can be eliminated by the correct choice of grid material. Thus, for the residual gases normally found in vacuum systems, ionization gauges with either molybdenum or tantalum grids exhibit anomalous ion currents whilst gauges with tungsten or platinum grids do not. A practical form of grid utilizes platinum-clad molybdenum wire.
{"title":"Anomalous ion currents in Bayard-Alpert ionization gauges","authors":"R. Lawson","doi":"10.1088/0508-3443/18/12/312","DOIUrl":"https://doi.org/10.1088/0508-3443/18/12/312","url":null,"abstract":"A theory has been developed to account quantitatively for the anomalous ion-current behaviour which leads to errors in pressure measurement in Bayard-Alpert ionization gauges. The equilibrium anomalous ion current has been studied as a function of the gauge electron current and operating pressure. Analysis of the experimental results in the light of the theory yields values for the total atom and ion desorption probability per electron, the ion desorption probability per electron and the sticking coefficient of gas molecules on the grid surface. Though the theory suggests ways in which the pressure measurement error can be minimized, experiment shows that the error can be eliminated by the correct choice of grid material. Thus, for the residual gases normally found in vacuum systems, ionization gauges with either molybdenum or tantalum grids exhibit anomalous ion currents whilst gauges with tungsten or platinum grids do not. A practical form of grid utilizes platinum-clad molybdenum wire.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"1 1","pages":"1763-1771"},"PeriodicalIF":0.0,"publicationDate":"1967-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90802297","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 : 1967-12-01DOI: 10.1088/0508-3443/18/12/317
A. C. Wells, A. Chamberlain
Radioactive particles have been used to study deposition from airstreams on to vertical surfaces. Polystyrene spheres 5 μm in diameter incorporating 51Cr, tri-cresyl-phosphate droplets 21, 11 and 065 μm in diameter with 32P activity, and natural Aitken nuclei tagged with ThB (212Pb) were used. The deposition on to smooth surfaces by impaction from turbulent flow was compared with theoretical predictions. Deposition by Brownian motion was also important for the smaller particles, and the results were in accordance with the empirical law relating transport to the two-thirds power of the diffusivity of the particle. When the deposition surface was covered with filter paper it remained aerodynamically smooth, but the deposition of particles was greatly increased since roughness elements too small to disturb the viscous boundary layer of the airflow are nevertheless effective in removing particles from it.
{"title":"TRANSPORT OF SMALL PARTICLES TO VERTICAL SURFACES.","authors":"A. C. Wells, A. Chamberlain","doi":"10.1088/0508-3443/18/12/317","DOIUrl":"https://doi.org/10.1088/0508-3443/18/12/317","url":null,"abstract":"Radioactive particles have been used to study deposition from airstreams on to vertical surfaces. Polystyrene spheres 5 μm in diameter incorporating 51Cr, tri-cresyl-phosphate droplets 21, 11 and 065 μm in diameter with 32P activity, and natural Aitken nuclei tagged with ThB (212Pb) were used. The deposition on to smooth surfaces by impaction from turbulent flow was compared with theoretical predictions. Deposition by Brownian motion was also important for the smaller particles, and the results were in accordance with the empirical law relating transport to the two-thirds power of the diffusivity of the particle. When the deposition surface was covered with filter paper it remained aerodynamically smooth, but the deposition of particles was greatly increased since roughness elements too small to disturb the viscous boundary layer of the airflow are nevertheless effective in removing particles from it.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"12 1","pages":"1793-1799"},"PeriodicalIF":0.0,"publicationDate":"1967-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84263808","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 : 1967-12-01DOI: 10.1088/0508-3443/18/12/314
M. Sugawara
The power dissipated at the wire anode of a d.c. arc discharge (10 A) has been measured, for arcs in argon at atmospheric pressure, by noting the length of the anode which is melted. The heating of the anode is due to electrons accelerated by the anode fall, the heat energy of the electrons and the work function of the anode material. The measurement of the power transferred by the electrons if the electron energy and the work function are known gives rise to a useful means of determining the anode fall.
{"title":"Anode melting caused by a d.c. arc discharge and its application to the determination of the anode fall","authors":"M. Sugawara","doi":"10.1088/0508-3443/18/12/314","DOIUrl":"https://doi.org/10.1088/0508-3443/18/12/314","url":null,"abstract":"The power dissipated at the wire anode of a d.c. arc discharge (10 A) has been measured, for arcs in argon at atmospheric pressure, by noting the length of the anode which is melted. The heating of the anode is due to electrons accelerated by the anode fall, the heat energy of the electrons and the work function of the anode material. The measurement of the power transferred by the electrons if the electron energy and the work function are known gives rise to a useful means of determining the anode fall.","PeriodicalId":9350,"journal":{"name":"British Journal of Applied Physics","volume":"13 1","pages":"1777-1781"},"PeriodicalIF":0.0,"publicationDate":"1967-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77586824","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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