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1995[X]
101Author    Christina Papenfußa, Jozsef Verhásb, Wolfgang MuschikaRequires cookie*
 Title      
 Abstract    A continuum theory of a biaxial nematic phase in liquid crystals is presented. The liquid crys­ talline ordering is described by a field of three unit vectors. Because these are macroscopic directors, the present approach is a generalization of the Ericksen-Leslie theory to biaxial nematics. The applied tools from nonequilibrium thermodynamics are classical Linear Irreversible Thermodynam­ ics and Gyarmati's variational principle. Onsager reci­ procity relations; Gyarmati's variational principle. A S im p lifie d T h e rm o d y n a m ic T h e o r y f o r B ia x ia l N e m a tic s 
  Reference    Z. Naturforsch. 50a, 795—804 (1995); received June 3 1994 
  Published    1995 
  Keywords    Liquid crystals, biaxial nematics, Linear Irreversible Thermodynamics 
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 TEI-XML for    default:Reihe_A/50/ZNA-1995-50a-0795.pdf 
 Identifier    ZNA-1995-50a-0795 
 Volume    50 
102Author    GurpreetK G Ill\, R. K. Chhabrab, S. K. TrehanRequires cookie*
 Title     
 Abstract    u b b le F o r m a tio n in S u p e rp o s e d M a g n e tic F lu id s in th e P r e s e n c e o f H e a t a n d M a s s T r a n s f e r In this paper we study the nonlinear Rayleigh-Taylor instability in the case of magnetic fluids in the presence of heat and mass transfer. We find that there is a normal field instability in the linear case. The behaviour of the bubbles in the nonlinear analysis is the same as if they were leaving the surface when the liquid is superheated. The criterion for "Explosive Instability" is also examined. 
  Reference    Z. Naturforsch. 50a, 805—812 (1995); received March 27 1995 
  Published    1995 
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 Identifier    ZNA-1995-50a-0805 
 Volume    50 
103Author    H. K. WagenfeldRequires cookie*
 Title      
 Abstract    Von Laue reformulated Ewald's dynamical theory of X-ray diffraction in crystals by solving Maxwell's equations for an electric susceptibility which has the periodicity of the crystals lattice. Absorption was in the original paper not included. Kohler showed that in this case the electric susceptibility is directly proportional to the electron charge density within the crystal. Von Laue assumed that the divergence of the electric field vector E is equal to the electron charge density which is excited by the electromagnetic field, and this is in accordance with Lorentz' classical electron theory. Under this assumption E is in contrast to D not a transverse wave. This is the reason that von Laue derived the fundamental equations in terms of D, and in order to obtain a simple wave equation he used the approximation 4nP=xD. Here P is the vector of the electric polarization and X is 471 times the electric susceptibility. This approximation is well justified, and von Laue's formulation is used in most publication on this subject. However some authors derived the fundamental equations in terms of fusing the correct relation \n P -x E . In most publications they assumed that the longitudinal component of the vector E is small and neglected it. This point and the comparison with von Laue's formulation was discussed by Miyake and Ohtsuki. We show here that the divergence of fcan be put zero if inelastic processes are excluded. This follows from Kohler's and Moliere's papers on the wave mechanical foundation of the dynamical theory of X-ray diffraction. However if higher perturbation terms are taken into account then the divergence of E differs from zero. In multiple beam cases the fundamental equations are much simpler if they are expressed in terms of E. In the region of anomalous dispersion, and here in particular in the region where the X-ray energy is close and above and crystal absorption edge, the wave equations should be expressed in terms of the electric field vector E. 
  Reference    Z. Naturforsch. 50a, 813—816 (1995); received February 20 1995 
  Published    1995 
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 Identifier    ZNA-1995-50a-0813 
 Volume    50 
104Author    Younan Hua, C. T. YapRequires cookie*
 Title     
 Abstract    a lc u la tio n o f T h e o r e tic a l A lp h a C o e ffic ie n ts f o r X R F A n a ly s is o f M a jo r a n d M in o r E le m e n ts in I r o n -r ic h G e o lo g ic a l S a m p le s This paper introduces a method of calculating theorectical alpha coefficients for the X-ray fluorescence analysis of major and minor components in iron-rich samples. We choose a group of hypothetical standard samples whose average concentrations are those of the actual samples. The theoretical X-ray fluorescence relative intensities of the given components are calculated using the fundamental parameter NRLXRF program. We derived formulas from the Lachance-Traill equa­ tion and used these to calculate the basic, hybrid and modified alpha coefficients which are used respectively for the analysis of elements in compact specimens, oxides in compact specimens and oxides in diluted specimens. In order to use the theoretical alpha coefficients on-line, we also discuss the calculation of the alpha coefficients used in the D.J model. 
  Reference    Z. Naturforsch. 50a, 817—825 (1995); received December 14 1994 
  Published    1995 
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 Identifier    ZNA-1995-50a-0817 
 Volume    50 
105Author    Z. NaturforschRequires cookie*
 Title      
 Abstract    The pressure-dependence of the dielectric anisotropy, Ae = e0||— e0±, of two nematogens, n-pentyl-and n-hexyl-cyanobiphenyl (5CB and 6CB) has been measured at constant temperature. For this purpose a high pressure chamber made of non-magnetic materials was constructed, allowing for the orientation of the samples by a magnetic field. The pressure dependencies of Aex were analyzed in the frame of the Maier-Meier equations for the principal permittivity components in the nematic phase. It was found that the relation between Ae and the order parameter S is not properly described by these equations. The Kirkwood correlation factor calculated on the basis of the present results and the Maier-Meier equations is smaller than 0.5, whereas it increases to a more realistic value (~0.7) if the electronic polarization is incorporated in the equations. P r e s s u r e D e p e n d e n c e o f th e D ie le c tric A n is o tr o p y o f 5 C B a n d 6 C B 
  Reference    Z. Naturforsch. 50a, 826—830 (1995); received April 28 1995 
  Published    1995 
  Keywords    Nematic liquid crystals, Cyanobiphenyls, High pressure, Dielectric anisotropy 
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 Identifier    ZNA-1995-50a-0826 
 Volume    50 
106Author    P. M. Hagenmayer3, S. Lamparterb, SteebbRequires cookie*
 Title     
 Abstract    The molten alloys Au28 5Mn71 5 and Au68Mn32 are investigated with the energy dispersive X-ray diffraction method which works rather fast so that the evaporation loss of Mn from the molten alloys is kept low. From the observed prepeak follows that both melts are compound-forming but the gold rich melt Au68Mn32 shows only 50% of the short range order existent within the Au28 5Mn71 5 melt. Total structure factors and total pair correlation functions are discussed. X -R a y D if fr a c tio n w ith M o lte n A u xM n 100_ x-A llo y s 
  Reference    Z. Naturforsch. 50a, 831—836 (1995); received June 1 1995 
  Published    1995 
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 Identifier    ZNA-1995-50a-0831 
 Volume    50 
107Author    M. Feike, K. Meise-Gresch, Qi Chen, G. H. FrischatRequires cookie*
 Title      
 Abstract    Dedicated to Professor Werner Müller-Warmuth on the occasion of his 65th birthday The annealing history of glasses in the system (20-40) BaO-40Ti02(40 -20)Si02 has been mon­ itored by 29Si MAS NMR and FTIR spectroscopy from the dried gel to the final glassy state. Assignment of chemical shifts to specific building units has been facilitated by comparative studies of the limiting less complex binary silicate systems. From the NMR spectra at various compositions appreciable condensation to a three-dimensional network is inferred already at low drying temper­ atures. Processes like the pyrolysis of acetate rests of the starting materials and modification of the silicate structure due to Ba cations have been mirrored in the spectra of both methods for samples annealed at intermediate temperatures. The microstructure of the final gel glass of the ternary system has been determined spectroscopically to consist of silicate and titanate species typical of crystalline fresnoite, whereas remaining amounts of TiOz and SiO? develop a separate network each. Only small amounts of Si-O-Ti linkages have been recognized in the vibrational absorptions; they vanish at higher annealing stages. 
  Reference    Z. Naturforsch. 50a, 837—844 (1995); received January 5 1995 
  Published    1995 
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 Identifier    ZNA-1995-50a-0837 
 Volume    50 
108Author    G. J. Krüger, A. BirkeRequires cookie*
 Title     
 Abstract    u c le a r M a g n e tic R e s o n a n c e M e a s u r e m e n ts in O il-N itr o g e n T w o -P h a s e F lo w Herrn Prof. Werner Müller-Warmuth zum 65. Geburtstag gewidmet in Erinnerung an langjährige fruchtbare Zusammenarbeit NMR measurements of the oil mass flow have been carried out in all-oil flow as well as in oil-nitrogen two-phase flow. For the calibration a simplified method was used which circumvents spin-lattice relaxation calculations due to the short polarization time of the protons at rather high flow velocities. With this method an overall accuracy of the oil-flow in oil-nitrogen two-phase flow of about ±5% was achieved. Some proposals for an improvement of the NMR apparatus are made, which would render the evaluations simpler and more accurate. 
  Reference    Z. Naturforsch. 50a, 845—851 (1995); received May 11 1995 
  Published    1995 
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 Identifier    ZNA-1995-50a-0845 
 Volume    50 
109Author    AlbertH. Bahnmaier, HaroldJones LaseranwendungenRequires cookie*
 Title     
 Abstract    o ta tio n a l R e s o lu tio n in th e V U V -S p e c tr u m o f C F 3I v ia I n f r a r e d -U ltr a v io le t D o u b le R e s o n a n c e E x p e r im e n ts This paper reports the double resonance signal observed by combination of a cw C 0 2 laser with a pulsed uv ionisation technique (REMPI). The infrared laser was used to pump a single ro-vibra-tional transition of the vx band of CF3I, and the resulting change in the two-photon, vuv spectrum was observed. Signals were detected under conditions of mass selectivity using a time of flight mass spectrometer. Previously unpublished data from infrared-microwave double resonance experiments are also included. 
  Reference    Z. Naturforsch. 50a, 852—856 (1995); received May 10 1995 
  Published    1995 
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 Identifier    ZNA-1995-50a-0852 
 Volume    50 
110Author    S. J. Cyvin3, J. Brunvolla, B. N. Cyvin3, W. LüttkebRequires cookie*
 Title      
 Abstract    Alkanoid systems are chemical graphs which can be embedded in the diamond lattice. They correspond to the staggered conformers of alkanes. Non-overlapping and overlapping systems are defined. The previously deduced algebraic solution for the numbers of unbranched alkanoids is revisited and reformulated in terms of generating functions. Computerized enumerations for non-overlapping alkanoids, both unbranched and branched, are reported. Some of the smallest overlap­ ping unbranched alkanoids are generated by a method called combinatorial constructions., E n u m e r a tio n o f th e S ta g g e r e d C o n f o r m e r s o f A lk a n e s 
  Reference    Z. Naturforsch. 50a, 857—863 (1995); received March 8 1995 
  Published    1995 
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 Identifier    ZNA-1995-50a-0857 
 Volume    50 
111Author    P. Krajnik1, R. M. Quint1, S. Solar1, N. Getoff1, G. Sontag2Requires cookie*
 Title      
 Abstract    flu e n c e o f T e m p e r a tu r e a n d O x y g e n C o n c e n tr a tio n o n th e R a d ia tio n In d u c e d O x id a tio n o f P h e n y la la n in e The formation of tyrosine isomers by y-radiolysis of neutral aqueous phenylalanine solutions was found to be strongly dependent on oxygen concentration and temperature. Changing the dose rate did not influence the degradation process. In the presence of 0.25 x 10-3 mol dm-^ oxygen at room temperature the yields of o-tyrosine as well as of m-and p-tyrosine drop from G(o-Tyr) = 0.5 and G(m-Tyr) = G(p-Tyr) = 0.4 at a dose of 0.3 kGy to 0.18 and 0.16 at 2.5 kGy, respectively. In solutions containing 1.25 x 10"3 mol dm-3 oxygen the initial yields remain unchanged but decrease at 2.5 kGy only to G(o-Tyr) = 0.3 and G(m-Tyr) = G(p-Tyr) = 0.20. Under the latter reaction condi­ tions also 3,4-dihydroxyphenylalanine was found. Samples irradiated in frozen state did not show remarkable radiolysis of phenylalanine and tyrosine formation. In the range between 5 and 20 °C no essential influence of temperature on the phenylalanine radiolysis and tyrosine yields was observable. The obtained results are important for methods using the tyrosine yields as markers for the detection of irradiated food. Storage conditions and irradiation temperature play an essential role on radiation induced changes of food. 
  Reference    Z. Naturforsch. 50a, 864—870 (1995); received July 3 1995 
  Published    1995 
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 Identifier    ZNA-1995-50a-0864 
 Volume    50 
112Author    Hisashi Honda, Shin'. Ichi Ishimaru, Noriko Onoda-Yamamuro, Ryuichi IkedaRequires cookie*
 Title     
 Abstract    y n a m ic s o f N i t r i te I o n s in th e I o n ic P la s tic C r y s ta l T IN O 2 s tu d ie d b y 15N a n d 205T1 N The temperature dependences of the NMR spin-lattice and spin-spin relaxation times and the NMR spectra of 15N in T115N02 were observed in the plastic phase (282.4 K < T < 459 K) and the low-temperature phase. From the analysis of 15N NMR data, we attributed the motion reported in dielectric and TI NMR studies in the low-temperature phase to the 180°-flip of NO^~ ions which takes place with an activation energy of 14 kJ mol-1. In the plastic phase, we detected isotropic NOJ reorientation with an activation energy of 13.5 kJ mol-1 and a new anionic motion with 10 kJ mol-1. 
  Reference    Z. Naturforsch. 50a, 871—875 (1995); received June 16 1995 
  Published    1995 
  Keywords    Solid NMR, Spin-lattice relaxation, Plastic crystal, Phase transition, Chemical shift anisotropy 
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 Identifier    ZNA-1995-50a-0871 
 Volume    50 
113Author    Hiroyuki Ishida, Hironobu Maeda, Akiko Hirano, Tamotsu Fujimoto, Yoshihiro Kubozono, Setsuo Kashino, Shuichi EmuraRequires cookie*
 Title    E X A F S S tu d y o n th e P h a s e T r a n s itio n ( P h a s e a ' -5) in C H 3 N H 3 I  
 Abstract    The local structure of CH3NH3I around the I" ion in Phase a 'and 8 was studied by iodine K-edge EXAFS. The crystal structure in Phase a ' was redetermined by single crystal X-ray diffraction. The Debye-Waller factor <r(2) derived from EXAFS spectra shows an anomalous behavior around the order-disorder transition temperature from Phase 8 to a '. The phase transition has been interpreted as the disordering process which involves not only the H atoms but also the C atoms in the cation. 
  Reference    Z. Naturforsch. 50a, 876—880 (1995); received June 16 1995 
  Published    1995 
  Keywords    Crystal structure, EXAFS, Phase transition, X-ray diffraction 
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 Identifier    ZNA-1995-50a-0876 
 Volume    50 
114Author    Svend Sievertsen, Lutz Galich, Heiner HomborgRequires cookie*
 Title     
 Abstract    l e c t r o n i c R a m a n S p e c tr a o f a L o w -S p in F e r a P o r p h y r i n a n d R e e x a m in a tio n o f th e V ib r a t i o n a l S p e c tr a o f K 3[F e (C N)6] a n d [F e (C 5H 5)2]B F4 The resonance Raman spectra of (nBu4N)[Fe(CN)2TPP] (("BiitN): tetra(n-butyl)ammonium; TPP: m-tetraphenylporphyrin), K3 [Fe(CN)6] and [Fe(C5H5)2]BF4 have been investigated. A molec­ ular electronic Raman (ER) effect at 545 cm"1 is observed for (nBu4N)[Fe(CN)2TPP]. The transi­ tion occurs between lower 'TV' and upper 'Tg" level of the spin-orbit split ground state assuming pseudo-octahedral symmetry. In contrast to earlier studies no ER effect is detected for K3[Fe(CN)6] and [Fe(C5H5)2]BF4. For Raman shifts < 800 cm-1 only one strong Raman line is observed for [Fe(C5H5)2]BF4 at 311 cm-1, assigned to the iron ring stretch designated by u4 (aig in D5(j). Due to a phase transition of K3[Fe(CN)6], two additional strong vibrational lines at 329 and 352 cm-1 appear in the Raman spectrum taken at 10 K. Their intensities show A "term" behaviour of the resonance Raman effect with overtones and combinations for both lines. These are components of the vibronic combinations with the i/6, vi, and i/g modes (tiu in Oh) in the IR spectra, too. 
  Reference    Z. Naturforsch. 50a, 881—887 (1995); received May 26 1995 
  Published    1995 
  Keywords    Di(cyano)-m-tetraphenylporphinatoferrate(III), Hexacyanoferrate(III), Ferricenium, Electronic Raman Spectra, Vibrational Spectra 
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 Identifier    ZNA-1995-50a-0881 
 Volume    50 
115Author    G. H., C. A., J. Zaleskia, G. Batorb, R. JakubasbRequires cookie*
 Title     
 Abstract    ie le c tr ic P r o p e r tie s a n d C h a r a c te r is a tio n o f th e S u p e rio n ic P h a s e o f [ C (N H 2) 3]2S b C l 5* [ C (N H 2) 3]C l (GHCA undergoes four phase transitions at Tcl = 402 K, Tc2 = 373 K, Ta = 162 K, and TcA = 146 K. Below Tc3 it possesses pyroelectric properties with the spontaneous polarization vector (Ps) in the ac plane and the maximum along the c axis equal to 8 pC/m2. Dielectric dispersion studies of GHCA show that the main dielectric dispersion connected probably with collective motions of chlorine ions is above 1GHz. For the phase transition at Tc2 to a superionic phase the thermal dilatation and electric conductivity were measured. The anomalies of the electric conductivity at Tc2 and T x were observed with large values of <j(10"3 S/m) above Tcl. The guanidinium cations above Tc2, besides reorientational motions, undergo slow self diffusion. 
  Reference    Z. Naturforsch. 50a, 888—892 (1995); received February 20 1995 
  Published    1995 
  Keywords    Guanidinium, chloroantimonate, phase transition, DSC, dilatometric, pyroelectric, electric conductivity 
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 Identifier    ZNA-1995-50a-0888 
 Volume    50 
116Author    T. A. Mirnaya, G. G. Yaremchuk, S. V. VolkovRequires cookie*
 Title    P h a s  
 Abstract    e D ia g r a m s o f B in a ry S y s te m s o f S o m e A lk a li I s o -B u ty r a te s w ith O n e M e s o g e n ic C o m p o n e n t The phase diagrams of the binary mixtures of mesogenic potassium iso-butyrate with non-meso-genic lithium-, sodium-, and caesium iso-butyrate have been investigated by differential thermal analysis and hot stage polarization microscopy. The temperature and concentration ranges of liquid crystal formation have been established. Sodium and caesium iso-butyrate have been found to possess latent mesogenic properties. 
  Reference    Z. Naturforsch. 50a, 893—896 (1995); received April 11 1995 
  Published    1995 
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 Identifier    ZNA-1995-50a-0893 
 Volume    50 
117Author    V. M. BabovićRequires cookie*
 Title     
 Abstract    le c tro n P la s m a W a v es o n C y lin d ric a l S tr u c tu r e s a n d th e C o n c e p t o f a n E q u iv a le n t D ie le c tr ic The dispersion relation A0(a>, ß) = 0 of the azymuthally symmetric electron surface wave propa­ gating on a plasma column placed in a glass tube of thickness Ö and permittivity eg has a fairly complicated form, with several parameters involved in many clusters of Bessel functions of various orders, kinds and arguments. Much simpler is the dispersion relation Ao(co,/?) = 0 for the surface wave on a plasma cylinder in a homogeneous dielectric, but that situation is often inapplicable as a model in real experiments. However, one can reproduce the A0 dispersion curves starting from the Aq ones, conveniently choosing an equivalent glass permittivity e(ö,eg,ß) instead of the constant . We have proved that this procedure gives acceptable approximate results. The computations valid for an azimuthally symmetric surface wave are given and the necessary comparisons done. 
  Reference    Z. Naturforsch. 50a, 897—901 (1995); received May 22 1995 
  Published    1995 
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 Identifier    ZNA-1995-50a-0897 
 Volume    50 
118Author    C. Haas, G. Pretzier1, T. Neger, H. JägerRequires cookie*
 Title     
 Abstract    e te rm in a tio n o f P a r ti c le D e n s itie s a n d L in e P r o f ile s in P la s m a s by R e s o n a n c e I n te r f e r o m e tr y : A F e a s ib ility S tu d y u sin g C o m p u te r S im u la te d R e f r a c tiv ity D a t a The principles of resonance interferometry are described with regard to two applications: High accuracy particle density determination within plasmas and interferometrical determination of spectral line profiles. The usability of this technique is investigated numerically, and physical limits are given for the regions in which resonance interferometry may be employed successfully. The discussion and the results are helt general for making it possible to decide whether or not to apply this method for an actual problem. An example (an object being longitudinally homogeneous with respect to the direction of light: end-on observation) shows how to use the presented results for calculating the detection limits of the method for a given object geometry. 
  Reference    Z. Naturforsch. 50a, 902—914 (1995); received April 8 1995 
  Published    1995 
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 Identifier    ZNA-1995-50a-0902 
 Volume    50 
119Author    Siegfried Grossmann, Sabine RanftRequires cookie*
 Title      
 Abstract    Two recently introduced methods to analyze heart beat are checked by applying them to numer­ ically produced time series representing artificial heart beat. The phase space diagram method (G. E. Morfill, G. Schmidt) depends on the variability of the sinus rhythm and the coupling interval of the extrasystoles. The risk index method (J. Kurths et al.) seems to measure different aspects of heart beat. D y n a m ic M o d e llin g o f H e a r t B e a t 
  Reference    Z. Naturforsch. 50a, 915—920 (1995); received July 10 1995 
  Published    1995 
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 Identifier    ZNA-1995-50a-0915 
 Volume    50 
120Author    Siegfried Grossmann, Martin Holthaus1Requires cookie*
 Title      
 Abstract    We study Bose-Einstein condensation of comparatively small numbers of atoms trapped by a three-dimensional harmonic oscillator potential. Under the assumption that grand canonical statis­ tics applies, we derive analytical expressions for the condensation temperature, the ground state occupation, and the specific heat capacity. For a gas of TV atoms the condensation temperature is proportional to iV1/3, apart from a downward shift of order iV~1/3. A signature of the condensation is a pronounced peak of the heat capacity. For not too small N the heat capacity is nearly discon­ tinuous at the onset of condensation; the magnitude of the jump is about 6.6 Nk. Our continuum approximations are derived with the help of the proper density of states which allows us to calculate finite-AT-corrections, and checked against numerical computations. 
  Reference    Z. Naturforsch. 50a, 921—930 (1995); received September 8 1995 
  Published    1995 
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 Identifier    ZNA-1995-50a-0921 
 Volume    50 
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