The electrical resistivity of amorphous carbon films getter-sputtered at 95°K is well fitted between 300 and 20°K by the relation with T0 ? 7 × 107K. This behavior suggests a hopping conductivity very similar to that found in other amorphous semiconductors. 相似文献
The birefringence of KMnF3 was measured in a temperature range between 130 and 186°K. It is shown that the birefringence is proportional to the square of displacement of F- ion and fits closely to near the transition point, where Ta lies at about 1.5°K above the transition temperature. Values of the order parameter are determined at each temperature. 相似文献
Electron spin resonance relaxation times were measured for the radiation induced radical ion SeO43? in selenium doped KDP single crystals. The spin-lattice relaxation time was found to obey the relation from 7 K to 200 K except in the neighborhood of the transition temperature where the data fit the expression T1?1 = T1R?1b±T ? Tcm± where θ is the Debye temperature and the plus and minus signs refer to data at temperatures above and below Tc respectively. 相似文献
We report the result of the Co59 nuclear spin-lattice relaxation time T1 measurements in the diamagnetic monoboride CoB. The analysis of the data, in the 4.2–300 K temperature range, allows us to separate three contributions to the relaxation rate: first a Korringa process, (T1KT)?1= 0.21 sec?1K?1 (in good agreement with the temperature independent isotropic Knight shift) from which we deduced the Co59 hyperfine constant A=6.2 ×10?6eV, second an impurity contribution independent of temperature and third a quadrupolar term, , which is predominant at high temperature and well explained by the Van Kranendonk theory. It seems that it was the first time that such a quadrupolar effect was detected in a metallic compound. A remarkable coherency between Lundquist's three bands model and our experimental results has to be noted. 相似文献
The sound velocities in GeS2 glass have been measured by means of ultrasonic interferometry as a function of temperature or pressure up to 1.8 kbar. The bulk modulus Ks = 117.6 kbar and shear modulus G = 60.60 kbar were obtained for GeS2 glass at 15°C and 1 atm. The temperature derivatives of both sound velocities and elastic moduli are negative : p = °C, p = °C and p = , p = ?1.23 × 10?2 kbar/°C, p = ?2.93 × 10?2 their pressure derivatives are positive: T = 4.43× 10?2km/kbar, T = and (?Ks?P0)T=6.81, = 1.03, (?Y?TT= 3.57. The Grüneisen parameter, γth= 0.298, and the second Grüneisen parameter, δs = 3.27, have also been calculated from these data. The elastic behavior of GeS2 glass has proved to be normal despite the structural similarity among the tetrahedrally coordinated SiO2, GeO2 and GeS2 glasses. 相似文献
We studied the energy width and the width in reciprocal space Δq of the central mode of SrTiO3 above Tc. At Tc+4° we observed an energy width of about 6×10?7 eV. If the measured Δq is interpreted by a correlation length we obtain . 相似文献
Preliminary results on electron drift velocity in neon gas at T = 293 K and T = 77.4 K are reported. At the lower temperature, values of field-independent mobility at five different densities have been obtained. From these data the momentum-transfer cross section at ? = 0.01 eV can be calculated to be . 相似文献
Some spectroscopic properties of the low-energy electronic states of 9-fluorenone have been examined. The spectra in paraffin matrices at 4.2°K show detailed vibrational spectra. Two fluorescence spectra are observed; a diffuse emission arises from 9-fluorenone crystals in the paraffin matrix, and a sharp emission is characteristic of the molecule. The sharp fluorescence is analyzed in terms of known a1 vibrational fundamentals. The sharp absorption is a near mirror-image to the fluorescence, so Herzberg-Teller vibrations are not prominent. The polarization in the crystal spectrum allows this low-energy transition near 23 000 cm?1 to be assigned . Because there is no vibronic perturbation in fluorescence, and certainly no out-of-plane modes, a transition seen at about 26 000 cm?1 is tentatively assigned . Another sharp absorption system is seen at 31 000 cm?1 in the paraffin matrices at 4.2°K (linewidth 6 cm?1) but no fluorescence was detected. The polarized crystal spectrum indicated the assignment of this system and another very strong system at 40 000 cm?1 to be , while other systems at about 34 000 cm?1 and 44 000 cm?1 are .The phosphorescence spectrum of pyrene-d10 held in a single crystal of 9-fluorenone at 4.2°K has been recorded. No delayed fluorescence from the host crystal is observed at 4.2°K but is intense at 77°K. The energy difference between host and guest triplet levels is estimated to be about 900 cm?1 allowing the lowest triplet state of 9-fluorenone to be placed at 17 800 cm?1. 相似文献
The emission and excitation spectra of the aromatic thioketone xanthione have been measured in Shpolskii matrices at 15 K. Under these conditions a sharp and rich vibrational structure is observed in the lowest triplet and the first and second excited singlet states. The phosphorescence excitation spectrum places the origin of the T1 ← S0 transition at 15 143 cm?1, while that of the absorption is tentatively assigned to the band at 16 093 cm?1. The phosphorescence spectrum, which shows only a weak CS stretch vibrational band, is dominated by ring vibrations. In accordance with the previous analysis of ODMR measurements, it is suggested that T1 and T2 states are energetically very close, thereby resulting in a lowest triplet state of heavily mixed n, , character. No mirror-image relationship is found between the relatively strong S2 → S0 fluorescence and the excitation spectrum of the transition. The latter is dominated by a long, pronounced 336-cm?1 progression. 相似文献
The time dependence of microwave absorption was measured for the J = 2-1 and J = 3-2 transitions of OCS under on- and off-resonant conditions utilizing Stark and source modulation, respectively. The two effective pressure parameters obtained under the two conditions, which correspond to and , respectively, according to the Bloch equation, are different beyond experimental error; the difference is 0.94 ± 0.38 (2.5σ) MHz/Torr for J = 2?1. This difference was also determined to be 1.19 ± 0.30 MHz/Torr from the dependence of the nutation frequency on the microwave power. 相似文献
Amorphous Fe40Ni40B20 (VITROVAC 0040) alloy has been investigated using 57Fe Mössbauer Spectroscopy. The Curie temperature Tc is found to be well defined and is 695 ± 1 K. The quadrupole splitting just above Tc is 0.64 mm sec?1. The crystallization temperature is 698 ± 2 K, close to but definitely above Tc. The average hyperfine field Heff(T) of the glassy state shows a temperature dependence of indicative of the existence of spin wave excitations. The values of and are found to be 0.40 and 0.06, respectively, for T/Tc ? 0.72. At temperatures close to Tc, Heff(T) varies as (1 ? T/Tc)β where β is one of the critical exponents and its value is found to be 0.29 ± 0.02. 相似文献
Spin lattice relaxation T1 of naturally abundant 13C nuclei in squaric acid was measured close to the antiferroelectric-paraelectric phase transition temperature Tc = 373 K. A rapid increase in is observed close to Tc coming from above, which follows the power law where . This behaviour is explained on the basis of the two-dimensional character of the fluctuations. 相似文献
The helicity, h?, of μ? in π-decay has been determined as positive (h??+0.90) from the average polarization, Pav≡〈JB·sμ〉, of 12B produced in the reaction. We obtain also dynamical information on μ-capture: (i) the weak magnetism form factor, μ=4.5±1.1, and (ii) the sum of the induced pseudoscalar (gp) and the 2nd class induced tensor (gT) couplings versus gA, (. The latter result, adopting the “canonical” value of , leads to which is compatible with zero and in strong contradiction with the value ?—6 recently advocated by Kubodera, Delorme and Rho. 相似文献
The inclusive production of and Ξ? hyperons is investigated in K+ p interactions at 32 GeV/c. The production cross sections, 36.4±9 μb for the and 6.5±3 μb for the Ξ?, are rising strongly with energy similarly to and Λ production in K+ p interactions. The are produced preferentially in the forward direction in the c.m.s., while the Ξ? are produced dominantly backwards. The average transverse momenta and 〈pT〉Ξ?=0.58±0.09 GeV/c. 相似文献
Transition temperature to LRO state was found at TN=1.14K for nearly one-dimensional antiferromagnet CuCl2 · 2NC5H5. Intra- and inter-chain exchange constants J and J′ were estimated, and , respectively. Comparison with those of TMMC implies highly one-dimensional character. 相似文献
The Coriolis interactions between ν1 and ν3, and between ν2 and ν3 in SO2 have been analyzed to obtain the signs of the products and . It has been found that both of the signs of these products are positive. Then, relative signs of () have been determined using the calculated values of the Coriolis zeta constants for the present definition of the normal coordinates. The obtained sign combination of () is ±(+?+), which agrees with the one predicted by the molecular orbital calculations. Using the sign combination (+?+), the polar tensors of S and O atoms were also calculated. 相似文献
Using the similarity of the effective potentials seen by ions in metals a reduced phonon equation of state is derived. It is shown that the melting point Tm(0) and the atomic volume Ω0 at T = 0 K and at p = 0 are suitable macroscopic parameters for scaling ? and σ characterizing the interatomic potentials of metals having similar structures. The temperature and pressure dependence of thermodynamical quantities reduced with the above parameters are discussed and the results are compared with the experiment. It is shown that the pressure dependence of the reduced thermodynamic quantities can be described by the pressure dependence of the scaling parameters Tm(p) and Ω0(p).The general form of the reduced equation of state (containing the electronic contributions as well) obtained gives that the reduced pressure is a universal function of the following reduced variables: the volume, temperature, de Broglie wavelength, Gibbs free energy of electrons (Efo is the Fermi energy at T = 0 K) and depe of the valence z as well. It is shown that is a function of and is approximately constant within the same sub-group of the periodic table. 相似文献
The catalytic decomposition of formic acid by a polycrystalline platinum surface was studied by use of modulated molecular beam techniques with mass spectrometric phasesensitive detection. Kinetic information about elementary surface reaction steps was obtained. The formation of CO2 was found to be a monomolecular, whereas that of D2 was a bimolecular process. The resulting reaction mechanism may be described as follows: The rate constants in dependence from the surface temperature t0 are The sticking probability η is provided by the temperature dependence of the intensity of the nonreactive scattered formic acid molecules; the rate constants kd1 and kd2 are derived from the measured phase shift between reactive and nonreactive scattered particles. From the phase angle ?, the average surface residence time τ of the intermediates is computed: 3.7 ? τDCOO ? 0.41 msec (418 ? T0 ? 505 K), 31.8 ? τD ? 11.6 msec (418 ? T0 ? 460 K). The difference between τD and τDCOO is because of the different molecularity of desorption. 相似文献
Spectral profiles of the 4607.33 Å Sr emission line were measured with a pressure-scanned Fabry-Pérot interferometer in a set of pre-mixed, laminar shielded H2/O2/Ar flames at 1 atm with temperatures ranging from 1765 to 2365 K. Some additional integrated line profile measurements were carried out.From the full width at one-half maximum (FWHM), δλT, and shift of the optically thin line profiles, adiabatic cross sections for broadening and for shift were determined for SrAr and SrH2O. 相似文献
The C33 constant is discontinuous for the lock-in transition at T1 = 169 K. The variation ΔT1 of the temperature of transition is a linear function of the applied electric field E and we find .Above a mean field E = 10 kV cm?1 the transition observed for a first heating spreads on several degrees because damages appear in the incommensurate phase and the electric field becomes inhomogeneous.The results obtained at low fields are in very good accordance with the value of calculated from the Clapeyron formula.Taking into account of the incommensurability of the phase above T1, it can be shown that The knowledge of the spontaneous polarisation P0 gives for the Curie constant C = 2.1 × 103 K in qualitative agreement with the value deduced from measurements of the dielectric constant in the ferroelectric direction. 相似文献