Journal De Physique最新文献_第8页

On the cohesion of small clusters of alkali metals 碱金属小簇的内聚力

Journal De Physique Pub Date : 1990-09-01 DOI: 10.1051/JPHYS:0199000510180202300

J. Friedel

引用次数: 1

Spectral diagnostic of a resonantly laser created non-Debye plasma 共振激光产生非德拜等离子体的光谱诊断

Journal De Physique Pub Date : 1990-09-01 DOI: 10.1051/JPHYS:0199000510180203300

J. Valognes, J. Bardet, C. Dimarcq, L. Giry

{"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}

引用次数: 2

Microscopic ordering in smectic phases of liquid crystals 液晶中近晶相的微观有序

Journal De Physique Pub Date : 1990-09-01 DOI: 10.1051/JPHYS:0199000510180201500

M. Zgonik, M. Rey-Lafon, C. Destrade, C. Leon, H. Nguyen

{"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}

引用次数: 12

Inelastic neutron scattering study of acoustic modes in a monodomain AlCuFe quasicrystal 单畴AlCuFe准晶声模的非弹性中子散射研究

Journal De Physique Pub Date : 1990-09-01 DOI: 10.1051/JPHYS:0199000510170178500

M. Quilichini, G. Heger, B. Hennion, S. Lefébvre, A. Quivy

引用次数: 29

Lamellar eutectic growth at large thermal gradient. II. Linear stability 在大热梯度下片层共晶生长。2。线性稳定

Journal De Physique Pub Date : 1990-09-01 DOI: 10.1051/JPHYS:0199000510170186500

B. Caroli, C. Caroli, B. Roulet

{"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}

引用次数: 16

Microscopic analysis of structure stabilities in the ionic compounds 离子化合物结构稳定性的微观分析

Journal De Physique Pub Date : 1990-09-01 DOI: 10.1051/JPHYS:0199000510180200500

B. Piveteau, C. Noguera

{"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}

引用次数: 0

First optical observation of Kossel diagrams in chiral smectic phases 手性晶相中科塞尔图的首次光学观察

Journal De Physique Pub Date : 1990-09-01 DOI: 10.1051/JPHYS:0199000510180208700

H. Kitzerow, G. Heppke, H. Schmid, B. Jérôme, P. Pieranski

{"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}

引用次数: 3

An algebraic semi-classical approach to Bloch electrons in a magnetic field 磁场中布洛赫电子的代数半经典方法

Journal De Physique Pub Date : 1990-09-01 DOI: 10.1051/JPHYS:0199000510170180300

R. Rammal, J. Bellissard

{"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}

引用次数: 66

Lamellar eutectic growth at large thermal gradient: I. Stationary patterns 大热梯度下的片层共晶生长:1 .固定模式

Journal De Physique Pub Date : 1990-09-01 DOI: 10.1051/JPHYS:0199000510170184700

K. Brattkus, B. Caroli, C. Caroli, B. Roulet

{"title":"Lamellar eutectic growth at large thermal gradient: I. Stationary patterns","authors":"K. Brattkus, B. Caroli, C. Caroli, B. Roulet","doi":"10.1051/JPHYS:0199000510170184700","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510170184700","url":null,"abstract":"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»","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"112 1","pages":"1847-1864"},"PeriodicalIF":0.0,"publicationDate":"1990-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87632093","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}

引用次数: 21

Recombinaison radiative directe le long de plusieurs séquences isoélectroniques 沿着几个等电子序列的直接辐射重组

Journal De Physique Pub Date : 1990-09-01 DOI: 10.1051/JPHYS:0199000510180207300

A. Poquérusse

引用次数: 0