An absorption spectrum in the range 200–220 nm, observed during the flash photolysis of Se2Br2, is attributed to SeBr. A vibrational analysis gives the following parameters of the states involved: X(2Πi): Te= 0 and 1070+a cm–1; ωe= 317 cm–1, ωexe= 0.7 cm–1, B: Te= 47 227 and 47 227+a cm–1; ωe= 393 cm–1, ωexe= 2.0 cm–1. An absorption spectrum due to TeI in the range 220–250 nm has been recorded in the flash photolysis of TeI2. The vibrational constants of the various states involved are: X(2Πi): Te= 0; ωe= 217 cm–1, ωexe= 0.6 cm–1. B: Te= 41 057 cm–1; ωe= 260 cm–1, ωexe= 1.4 cm–1. C: Te= 43 658 cm–1; ωe= 252 cm–1, ωexe= 0.5 cm–1.
{"title":"Ultra-violet spectra of SeBr and TeI","authors":"G. Oldershaw, K. Robinson","doi":"10.1039/TF9716700907","DOIUrl":"https://doi.org/10.1039/TF9716700907","url":null,"abstract":"An absorption spectrum in the range 200–220 nm, observed during the flash photolysis of Se2Br2, is attributed to SeBr. A vibrational analysis gives the following parameters of the states involved: X(2Πi): Te= 0 and 1070+a cm–1; ωe= 317 cm–1, ωexe= 0.7 cm–1, B: Te= 47 227 and 47 227+a cm–1; ωe= 393 cm–1, ωexe= 2.0 cm–1. An absorption spectrum due to TeI in the range 220–250 nm has been recorded in the flash photolysis of TeI2. The vibrational constants of the various states involved are: X(2Πi): Te= 0; ωe= 217 cm–1, ωexe= 0.6 cm–1. B: Te= 41 057 cm–1; ωe= 260 cm–1, ωexe= 1.4 cm–1. C: Te= 43 658 cm–1; ωe= 252 cm–1, ωexe= 0.5 cm–1.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"23 19 1","pages":"907-912"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716700907","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57617161","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}
A simple analysis of the degassing kinetics of metal wires is presented in order to examine the dependence of the rate of efflux of the dissolved gas on the physical and thermodynamic parameters of the system. In practice, the process often tends to be dominated either by the rate of diffusion of the gas within the metal, or by the desorption rate at the surface. There is, however, some indication that there are situations in which both factors may operate together.
{"title":"Degassing kinetics of metal wires","authors":"W. Lamb","doi":"10.1039/TF9716701137","DOIUrl":"https://doi.org/10.1039/TF9716701137","url":null,"abstract":"A simple analysis of the degassing kinetics of metal wires is presented in order to examine the dependence of the rate of efflux of the dissolved gas on the physical and thermodynamic parameters of the system. In practice, the process often tends to be dominated either by the rate of diffusion of the gas within the metal, or by the desorption rate at the surface. There is, however, some indication that there are situations in which both factors may operate together.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"1137-1142"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716701137","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57617692","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}
The anhydride resulting from the dehydration of manganous formate dihydrate is crystalline and its skeletal structure is distinct from the dihydrate. Under the proper conditions of temperature and water vapour pressure the freshly dehydrated anhydride rehydrates readily and completely to the dihydrate. Rehydration against time curves have been obtained for anhydrides prepared from the dihydrate which was in the form of individual single crystals, crystalline powder, ground powder and reactor-irradiated powder. The pressure, time and temperature dependences of the rehydration process have been determined. The extent of rehydration is described by a square-root dependence on time. This suggests that the rehydration is diffusion-controlled. The rate of rehydration increases markedly with pressure. Below a supersaturation ratio of approximately 10, rehydration does not occur; rather there is an appreciable sorption. The rate of sorption is diffusion-controlled with an energy of activation for diffusion of 12.0 kcal /mol. Isotherms have been determined for the sorbed water.
{"title":"Kinetics of rehydration of crystalline anhydrides. Manganous formate","authors":"R. Eckhardt, Peter M. Fichte, T. Flanagan","doi":"10.1039/TF9716701143","DOIUrl":"https://doi.org/10.1039/TF9716701143","url":null,"abstract":"The anhydride resulting from the dehydration of manganous formate dihydrate is crystalline and its skeletal structure is distinct from the dihydrate. Under the proper conditions of temperature and water vapour pressure the freshly dehydrated anhydride rehydrates readily and completely to the dihydrate. Rehydration against time curves have been obtained for anhydrides prepared from the dihydrate which was in the form of individual single crystals, crystalline powder, ground powder and reactor-irradiated powder. The pressure, time and temperature dependences of the rehydration process have been determined. The extent of rehydration is described by a square-root dependence on time. This suggests that the rehydration is diffusion-controlled. The rate of rehydration increases markedly with pressure. Below a supersaturation ratio of approximately 10, rehydration does not occur; rather there is an appreciable sorption. The rate of sorption is diffusion-controlled with an energy of activation for diffusion of 12.0 kcal /mol. Isotherms have been determined for the sorbed water.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"1143-1154"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716701143","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57618060","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}
The 35Cl n.q.r. frequencies of seven N-chloro molecules are reported and with those of five additional molecules in the literature, interpreted using BEEM and BEEM-π. The frequency is dependent on the hybridization of the N atom: with tr1tr1tr1π2 hybridized N the 35Cl frequency is around 55 MHz, with tr1tr1tr2π1hybridized N around 46 MHz and with te1te1te1te2 hybridized N at 44 MHz.
{"title":"35Cl nuclear quadrupole resonance of the N—Cl bond","authors":"R. Hart, M. Whitehead","doi":"10.1039/TF9716701569","DOIUrl":"https://doi.org/10.1039/TF9716701569","url":null,"abstract":"The 35Cl n.q.r. frequencies of seven N-chloro molecules are reported and with those of five additional molecules in the literature, interpreted using BEEM and BEEM-π. The frequency is dependent on the hybridization of the N atom: with tr1tr1tr1π2 hybridized N the 35Cl frequency is around 55 MHz, with tr1tr1tr2π1hybridized N around 46 MHz and with te1te1te1te2 hybridized N at 44 MHz.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"727 1","pages":"1569-1575"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716701569","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57620661","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}
Absolute rate constants for the reactions of the stable free radical triacetoneamine-N-oxyl (TAN) with a variety of radiation-induced radicals have been determined by direct observation or by competition methods. Like oxygen, TAN reacts rapidly with the electron adducts of acetophenone, thymine and nicotinamide adenine dinucleotide (k= 108-109 M–1 s–1) and reacts slowly, if at all, with the electron adducts of p-nitroacetophenone and benzoquinone. Absolute rate constants for the reaction of TAN with neutral aliphatic radicals are, in general, an order of magnitude lower than the analogous reactions with oxygen. Unlike oxygen, TAN also reacts with halide radical anions, X–2 at near diffusion-controlled rates.
{"title":"Pulse radiolysis studies on reaction of triacetoneamine-N-oxyl with radiation-induced free radicals","authors":"R. Willson","doi":"10.1039/TF9716703008","DOIUrl":"https://doi.org/10.1039/TF9716703008","url":null,"abstract":"Absolute rate constants for the reactions of the stable free radical triacetoneamine-N-oxyl (TAN) with a variety of radiation-induced radicals have been determined by direct observation or by competition methods. Like oxygen, TAN reacts rapidly with the electron adducts of acetophenone, thymine and nicotinamide adenine dinucleotide (k= 108-109 M–1 s–1) and reacts slowly, if at all, with the electron adducts of p-nitroacetophenone and benzoquinone. Absolute rate constants for the reaction of TAN with neutral aliphatic radicals are, in general, an order of magnitude lower than the analogous reactions with oxygen. Unlike oxygen, TAN also reacts with halide radical anions, X–2 at near diffusion-controlled rates.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"3008-3019"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716703008","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57631574","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}
The sorption, permeation and diffusion of water in a series of polyalkylmethacrylates has been studied for a number of temperatures in the range 298–353 K. In each case the diffusion coefficient decreased as the concentration of sorbed water was increased. The heat and the entropy of dilution decreased with concentration and the activation energy for diffusion increased. Polymethylmethacrylate was the exception in that both the heat of dilution and the activation energy for diffusion were independent of concentration. The results are consistent with significant clustering of the water molecules in the polymer matrix. A comparison is made with a random polycondensation model for the association of water through hydrogen-bond formation.
{"title":"Diffusion and association of water in some polyalkylmethacrylates. Part 1.—Equilibrium sorption and steady state permeation","authors":"J. A. Barrie, D. Machin","doi":"10.1039/TF9716700244","DOIUrl":"https://doi.org/10.1039/TF9716700244","url":null,"abstract":"The sorption, permeation and diffusion of water in a series of polyalkylmethacrylates has been studied for a number of temperatures in the range 298–353 K. In each case the diffusion coefficient decreased as the concentration of sorbed water was increased. The heat and the entropy of dilution decreased with concentration and the activation energy for diffusion increased. Polymethylmethacrylate was the exception in that both the heat of dilution and the activation energy for diffusion were independent of concentration. The results are consistent with significant clustering of the water molecules in the polymer matrix. A comparison is made with a random polycondensation model for the association of water through hydrogen-bond formation.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"244-256"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716700244","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57614087","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}
Processes of solid phase transition, fusion and decomposition in several nitramines (and a nitrosamine) have been investigated using differential scanning calorimetry. The following values (kcal mol–1) for the enthalpy changes, ΔH(TK) are reported: N-picryl-N-methylnitramine (tetryl), ΔHf(400.5)= 6.18±0.07, –ΔHd(445)= 94±2; 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX)ΔHf(478.5)= 8.52 ± 0.07, –ΔHd(483)= 136 ± 2; 1,3,5,7-tetranitro-1,3,5,7-tetra-azacyclooctane, (HMX), ΔHt,β→δ(ca. 460)= 2.35±0.20, –ΔHd(ca. 540)= 166±9; 1,7-diacetoxy-2,4,6-trinitro-2,4,6-triazaheptane (BSX), ΔHf(422.5)= 9.2 ±0.4, –ΔHd(ca. 500)= 124± 12; 1,5-endomethylene-3,7-dinitro-1,3,5,7-tetra-azacyclooctane (DPT), –ΔHd(ca. 471)= 35 ± 6; 1,3-dinitro-1,3-diazacyclopentane (DDCP), ΔHf(403)≃ 6.0; 1,3-dinitro-1,3-diazacyclohexane(DDCHX), ΔHt(343)= 3.7 ± 0.3, ΔHf(353)= 0.70 ±0.02; 1,3-dinitro-1,3-diazacycloheptane (DDCHP), ΔHt(370)≃ 5.6, ΔHf(376)≃ 0.95; 1,3,5-trinitroso-1,3,5-triazacyclohexane (TNOHX), ΔHt(365)= 4.25±0.15, ΔHf(376)= 0.90±0.03. The depression of the melting point of tetryl caused by pre-heating the solids is used together with literature data ((i) relating the melting point depression with the amount of gas produced during decomposition, and (ii) for the amount of gas produced on complete decomposition) to calculate first-order rate constants for decomposition in the region of the solid→liquid transition. The results indicate a “premonitory” effect at temperatures below the melting point. With the exception of RDX (apparent Ea= 45.2±0.4 kcal mol–1) the apparent activation energies for de-composition of the nitramines tend to be unrealistically high. DDCHX, DDCHP and TNOHX show plastic crystal behaviour and may be classified as “globular” molecules; the absence of this type of behaviour with DDCP and RDX is discussed in terms of factors affecting molecular rotation in the solid state.
{"title":"Thermal decomposition and phase transitions in solid nitramines","authors":"P. G. Hall","doi":"10.1039/TF9716700556","DOIUrl":"https://doi.org/10.1039/TF9716700556","url":null,"abstract":"Processes of solid phase transition, fusion and decomposition in several nitramines (and a nitrosamine) have been investigated using differential scanning calorimetry. The following values (kcal mol–1) for the enthalpy changes, ΔH(TK) are reported: N-picryl-N-methylnitramine (tetryl), ΔHf(400.5)= 6.18±0.07, –ΔHd(445)= 94±2; 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX)ΔHf(478.5)= 8.52 ± 0.07, –ΔHd(483)= 136 ± 2; 1,3,5,7-tetranitro-1,3,5,7-tetra-azacyclooctane, (HMX), ΔHt,β→δ(ca. 460)= 2.35±0.20, –ΔHd(ca. 540)= 166±9; 1,7-diacetoxy-2,4,6-trinitro-2,4,6-triazaheptane (BSX), ΔHf(422.5)= 9.2 ±0.4, –ΔHd(ca. 500)= 124± 12; 1,5-endomethylene-3,7-dinitro-1,3,5,7-tetra-azacyclooctane (DPT), –ΔHd(ca. 471)= 35 ± 6; 1,3-dinitro-1,3-diazacyclopentane (DDCP), ΔHf(403)≃ 6.0; 1,3-dinitro-1,3-diazacyclohexane(DDCHX), ΔHt(343)= 3.7 ± 0.3, ΔHf(353)= 0.70 ±0.02; 1,3-dinitro-1,3-diazacycloheptane (DDCHP), ΔHt(370)≃ 5.6, ΔHf(376)≃ 0.95; 1,3,5-trinitroso-1,3,5-triazacyclohexane (TNOHX), ΔHt(365)= 4.25±0.15, ΔHf(376)= 0.90±0.03. The depression of the melting point of tetryl caused by pre-heating the solids is used together with literature data ((i) relating the melting point depression with the amount of gas produced during decomposition, and (ii) for the amount of gas produced on complete decomposition) to calculate first-order rate constants for decomposition in the region of the solid→liquid transition. The results indicate a “premonitory” effect at temperatures below the melting point. With the exception of RDX (apparent Ea= 45.2±0.4 kcal mol–1) the apparent activation energies for de-composition of the nitramines tend to be unrealistically high. DDCHX, DDCHP and TNOHX show plastic crystal behaviour and may be classified as “globular” molecules; the absence of this type of behaviour with DDCP and RDX is discussed in terms of factors affecting molecular rotation in the solid state.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"556-562"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716700556","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57614881","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}
The rate of recombination of hydrogen atoms in fuel-rich hydrogen/oxygen/nitrogen flames containing metal additives has been measured using the lithium/lithium hydroxide method to monitor hydrogen atom concentrations. It is found that the rate of the recombination reaction is accelerated by the addition of alkaline earth metals. The preferred mechanism for catalysis is via the cycle of reactions: MOH + H →MO + H2(7), MO + H2O(+X)→M(OH)2(+X)(8), M(OH)2+ H⇌MOH + H2O (–5), and the rate of the catalyzed recombination is given by the expression [graphic omitted] Values of k7 and lower limits of k8 have been determined for calcium, strontium and barium at 1570 K and 1800 K. The upper limit for the catalysis to be effective is about 2000 K. This is determined by the increase of K5 with temperature.
采用锂/氢氧化锂法监测氢原子浓度，测定了含金属添加剂的富燃料氢/氧/氮火焰中氢原子的复合速率。结果表明，碱土金属的加入加快了复合反应的速度。优选的催化机理是通过反应循环:MOH + H→MO + H2(7)， MO + H2O(+X)→M(OH)2(+X)(8)， M(OH)2+ H + MOH + H2O(-5)，催化重组的速率由式给出[图略]在1570 K和1800 K下测定了钙、锶和钡的k7值和k8下限。有效催化的上限约为2000k。这是由K5随温度的增加决定的。
{"title":"Catalysis of radical-recombination reactions in flames by alkaline earth metals","authors":"D. Cotton, D. R. Jenkins","doi":"10.1039/TF9716700730","DOIUrl":"https://doi.org/10.1039/TF9716700730","url":null,"abstract":"The rate of recombination of hydrogen atoms in fuel-rich hydrogen/oxygen/nitrogen flames containing metal additives has been measured using the lithium/lithium hydroxide method to monitor hydrogen atom concentrations. It is found that the rate of the recombination reaction is accelerated by the addition of alkaline earth metals. The preferred mechanism for catalysis is via the cycle of reactions: MOH + H →MO + H2(7), MO + H2O(+X)→M(OH)2(+X)(8), M(OH)2+ H⇌MOH + H2O (–5), and the rate of the catalyzed recombination is given by the expression [graphic omitted] Values of k7 and lower limits of k8 have been determined for calcium, strontium and barium at 1570 K and 1800 K. The upper limit for the catalysis to be effective is about 2000 K. This is determined by the increase of K5 with temperature.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"730-739"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716700730","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57616231","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}
The adsorption and desorption of Cu on a smooth Pt electrode from 1 M H2SO4 solutions which contain a range of Cu2+ concentrations has been studied as a function of potential. The effect of adsorbed Cu on the oxidation rate of HCOOH has been examined at + 0.60 V (RHE). Cu2+ adsorption is controlled largely by an activation process. The slow step in the process is apparently the discharge of Cu2+ at the electrode to Cu+. Desorption of a preadsorbed Cu layer (+0.40 V) is extremely rapid at potentials+ 0.70 V, where no Cu2+ adsorption is normally found. Analysis of the oxidation state of the adsorbing layer by charge and coverage measurements yields a value of 1.92 electrons/site. This indicates that the major part of the layer is Cuads attached to a single Pt surface site. The rate of adsorption of Cu2+ is decreased slightly in the presence of 0.1 M HCOOH. At low coverages (θCuads⩽0.19), a slight enhancement of the HCOOH oxidation rate is observed at +0.60 V. Above this coverage, the oxidation process is inhibited. Results are interpreted in terms of Cu2+ adsorption mechanisms on Pt and the effect of the adsorbed layer on the mechanisms of HCOOH electro-oxidation on Pt.
本文研究了不同Cu2+浓度的H2SO4溶液对Cu在光滑Pt电极上的吸附和解吸过程。在+ 0.60 V (RHE)下，考察了吸附Cu对HCOOH氧化速率的影响。Cu2+吸附主要受活化过程控制。该过程的缓慢步骤显然是电极处的Cu2+向Cu+放电。在+ 0.70 V电势下，预吸附Cu层(+0.40 V)的脱附速度非常快，通常没有Cu2+吸附。通过电荷和覆盖率测量对吸附层的氧化状态进行分析，得出1.92个电子/位点的值。这表明该层的主要部分是附着在单个Pt表面的cuad。在0.1 M HCOOH的存在下，对Cu2+的吸附速率略有下降。在低覆盖率(θCuads≥0.19)下，在+0.60 V下观察到HCOOH氧化速率略有增强。在此覆盖范围以上，氧化过程被抑制。结果解释了Cu2+在Pt上的吸附机理，以及吸附层对HCOOH电氧化Pt机理的影响。
{"title":"Effect of adsorbed layers on the anodic oxidation of simple organic compounds. Part 3.—Cu adsorption on Pt and its effect on the oxidation of HCOOH","authors":"A. H. Taylor, S. Kirkland, S. Brummer","doi":"10.1039/TF9716700809","DOIUrl":"https://doi.org/10.1039/TF9716700809","url":null,"abstract":"The adsorption and desorption of Cu on a smooth Pt electrode from 1 M H2SO4 solutions which contain a range of Cu2+ concentrations has been studied as a function of potential. The effect of adsorbed Cu on the oxidation rate of HCOOH has been examined at + 0.60 V (RHE). Cu2+ adsorption is controlled largely by an activation process. The slow step in the process is apparently the discharge of Cu2+ at the electrode to Cu+. Desorption of a preadsorbed Cu layer (+0.40 V) is extremely rapid at potentials+ 0.70 V, where no Cu2+ adsorption is normally found. Analysis of the oxidation state of the adsorbing layer by charge and coverage measurements yields a value of 1.92 electrons/site. This indicates that the major part of the layer is Cuads attached to a single Pt surface site. The rate of adsorption of Cu2+ is decreased slightly in the presence of 0.1 M HCOOH. At low coverages (θCuads⩽0.19), a slight enhancement of the HCOOH oxidation rate is observed at +0.60 V. Above this coverage, the oxidation process is inhibited. Results are interpreted in terms of Cu2+ adsorption mechanisms on Pt and the effect of the adsorbed layer on the mechanisms of HCOOH electro-oxidation on Pt.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"809-818"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716700809","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57616462","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}
The absorption anisotropy of 1,2,4,5 tetramethylbenzene crystals in the region 33 000–40 500 cm–1 is investigated at room and liquid nitrogen temperature. The f-values for both directions of propagation of the light vector in the (001) face were measured and corrected for reflectivity losses. Frequency shifts of the absorption peaks and changes in f-values with temperature are discussed. Comparison of crystal absorption with oriented gas intensities leads to the conclusion that the transition is long-axis polarized. The assignment is discussed in relation to a calculation on crystal shift and Davydov splitting. The probable orientation and magnitude of the transition moment, induced by the crystal field in the unit cell, is indicated.
{"title":"Intensities in polarized light: near ultraviolet absorption spectrum of 1,2,4,5 tetramethylbenzene","authors":"A. Brillante, C. Zauli","doi":"10.1039/TF9716700913","DOIUrl":"https://doi.org/10.1039/TF9716700913","url":null,"abstract":"The absorption anisotropy of 1,2,4,5 tetramethylbenzene crystals in the region 33 000–40 500 cm–1 is investigated at room and liquid nitrogen temperature. The f-values for both directions of propagation of the light vector in the (001) face were measured and corrected for reflectivity losses. Frequency shifts of the absorption peaks and changes in f-values with temperature are discussed. Comparison of crystal absorption with oriented gas intensities leads to the conclusion that the transition is long-axis polarized. The assignment is discussed in relation to a calculation on crystal shift and Davydov splitting. The probable orientation and magnitude of the transition moment, induced by the crystal field in the unit cell, is indicated.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"913-921"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716700913","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57617171","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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