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1.
We present a two-dimensional model to account for the role of heat-conducting walls in the measurement of heat transport and Soret-effect-driven mass transport in transient holographic grating experiments. Heat diffusion into the walls leads to non-exponential decay of the temperature grating. Under certain experimental conditions it can be approximated by an exponential function and assigned an apparent thermal diffusivity Dth, app < Dth, s, where Dth,s is the true thermal diffusivity of the sample. The ratio Dth, app/Dth, s depends on only three dimensionless parameters, d /ls, κsw, and Dth, s/Dth, w. d is the grating period, ls the sample thickness, κs and κw the thermal conductivities of sample and wall, respectively, and Dth,w the thermal diffusivity of the wall. If at least two measurements are performed at different d /ls, both Dth,s and κs can be determined. Instead of costly solving PDEs, Dth,s can be obtained by finding the zero of an analytic function. For thin samples and large grating periods, heat conduction into the walls plays a predominant role and the concentration grating in binary mixtures is no longer one-dimensional. Nevertheless, the normalized heterodyne diffraction efficiency of the concentration grating remains unaffected and the true thermal and collective diffusion coefficient and the correct Soret coefficient are still obtained from a simple one-dimensional model.  相似文献   

2.
The high-resolution infrared spectrum of HCF3 was studied in the ν6 fundamental (near 500 cm−1) and in the 2ν6 overtones (near 1000 cm−1) regions. The present study reports on the analysis of the hot bands in the ν6 region, as well as the first observation and assignment of the 2ν62 perpendicular band. Using ν6, 2ν6±2ν6±1 and 2ν62 experimental wavenumbers, accurate coefficients C0 and DK0 of the K-dependent ground-state energy terms were obtained, using the so-called “loop method.” Ground-state energy differences Δ(K,J)=E0(K,J)−E0(K−3,J) were obtained for K=3–30. A least-squares fit of 81 such differences gave the following results (in cm−1): C0=0.1892550(15); DK0=2.779(26) × 10−7.  相似文献   

3.
New measurements are reported for the infrared spectrum of sulfur trioxide, 32S16O3, with resolutions ranging from 0.0015 cm−1 to 0.0025 cm−1. Rovibrational constants have been measured for the fundamentals ν2, ν3, and ν4 and the overtone band 2ν3. Comparisons are made with the earlier high-resolution measurements on SO3, and the high correlation among some of the constants related to the Coriolis coupling of the ν2 and ν4 levels is discussed in order to understand the areas of disagreement with the earlier work. Splittings of some of the levels are observed and the splitting constant for K=3 of the ground state is determined for the first time. Other observed splittings include the K=1 levels of 2ν3 (l=2), the K=2 levels of ν3 and ν4, and the K=3 levels of ν2. The analysis shows that there are level crossings between the l=0 and l=2 states of 2ν3 that allow one to determine the separation of the subband centers for these two states even though access to the l=0 state from the ground state is electric-dipole forbidden. This is a generalized phenomenon that should be found for many other molecules with the same symmetry. The l-type resonance constant, q3, that causes the splitting of the l3=±1, k=±1 levels of ν3 also couples the l3=0 and 2 states of 2ν3.  相似文献   

4.
Flavor symmetry and symmetry breaking, K0– mixing and possible effects of new physics on CP violation in weak decay modes D±KS,L+X±, (KS,L0)K*+X± (for X=π,ρ,a1) and D±sKS,L+X±s, (KS,L0)K*+X±s (for Xs=K,K*) are analyzed. Relations between D± and D±s decay branching ratios are obtained from the ds subgroup of SU(3) and dominant symmetry-breaking mechanisms are investigated. A CP asymmetry of magnitude 3.3×10−3 is shown to result in the standard model from K0– mixing in the final-state. New physics affecting the doubly Cabibbo-suppressed channels might either cancel this asymmetry or enhance it up to the percent level. A comparison between the CP asymmetries in D±(s)KSX±(s) and D±(s)KLX±(s) can pin down effects of new physics.  相似文献   

5.
《Physics letters. [Part B]》2005,610(3-4):183-191
The absolute branching fraction for the decay D+μ+ν has been directly measured based on a data sample of about 33 pb−1 collected around with the BES-II detector at the BEPC collider. A total of 5321±149±160 D mesons are reconstructed in nine hadronic decay modes. In the system recoiling against these singly tagged D mesons, 2.67±1.74 purely leptonic decay events of D+μ+νμ are observed. Those yield the branching fraction of , and a corresponding value of the pseudoscalar decay constant .  相似文献   

6.
The temperature dependence of ρxx is studied in the vicinity of the quantum Hall to quantum Hall insulator transition (ν=1→0) in InSb/InAlSb based 2DESs. ρxx displays a symmetric temperature dependence about the transition with on the QH side and on the insulating side. A plot of 1/T0 for successive ν displays power-law divergence with 1/T0∝|ν−νc|−γ,2 with γ=2.2±0.3. This critical behavior in addition to the behavior expected of the quantum transport regime confirms that the QH/QHI transition is indeed a good quantum phase transition.  相似文献   

7.
We study the q-state Potts model with nearest-neighbor coupling v=eβJ−1 in the limit q,v → 0 with the ratio w = v/q held fixed. Combinatorially, this limit gives rise to the generating polynomial of spanning forests; physically, it provides information about the Potts-model phase diagram in the neighborhood of (q,v) = (0,0). We have studied this model on the square and triangular lattices, using a transfer-matrix approach at both real and complex values of w. For both lattices, we have computed the symbolic transfer matrices for cylindrical strips of widths 2≤ L ≤ 10, as well as the limiting curves B of partition-function zeros in the complex w-plane. For real w, we find two distinct phases separated by a transition point w=w0, where w0 =−1/4 (resp. w0=−0.1753 ± 0.0002) for the square (resp. triangular) lattice. For w>w0 we find a non-critical disordered phase that is compatible with the predicted asymptotic freedom as w → +∞. For w0 our results are compatible with a massless Berker–Kadanoff phase with central charge c=−2 and leading thermal scaling dimension xT,1 = 2 (marginally irrelevant operator). At w=w0 we find a “first-order critical point”: the first derivative of the free energy is discontinuous at w0, while the correlation length diverges as w↓ w0 (and is infinite at w=w0). The critical ehavior at w=w0 seems to be the same for both lattices and it differs from that of the Berker–Kadanoff phase: our results suggest that the central charge is c=−1, the leading thermal scaling dimension is xT,1=0, and the critical exponents are ν=1/d=1/2 and α=1.  相似文献   

8.
The new molecule 1-phosphabut-3-ene-1-yne, CH2=CHCP, produced by pyrolyzing prop-1-ene-3-phosphorus dichloride, CH2=CHCH2PCl2, was detected by microwave spectroscopy. The analysis of the rotational transitions indicates that the molecule is planar with constants: A0 = 46 694(24), B0 = 2807.7100(21), and C0 = 2645.8356(21) MHz. These rotational constants indicate that the structure of the vinyl group is essentially the same as that in CH2=CHCN and CH2=CHCCH; r(C---C) = 1.432 Å and (C=C---C) = 123.9°. The dipole moment parameters are μA = 1.181(2), μB = 0.074(1), and μ = 1.183(2) D. The vibrational satellite spectra for the C---CP bending modes indicate that ν11(a′) = 184 ± 30 cm−1 and ν15(a″) = 263 ± 30 cm−1.  相似文献   

9.
We consider the renormalization of the twist two, dimension four gauge invariant operator Oμν(1) = − FμσFνσgμν 0. By using the general theory of renormalization of gauge invariant operators, we find the gauge noninvariant operator O(2) with which it mixes. We construct a finite combination of O(1) and O(2) and show that it is an acceptable energy momentum tensor for gauge theories. We compare our energy momentum tensor with that constructed by Freedman, Muzinich, and Weinberg.  相似文献   

10.
A new precise measurement of |Vcb| and of the branching ratio BR ) has been performed using a sample of about 5000 semileptonic decays , selected by the DELPHI detector at LEP I by tagging the soft pion from D*+D0π+. The results are: Vcb=(39.0±1.5 (stat.)+2.5−2.6 (syst. exp.)±1.3 (syst. th.))×10−3,

. The analytic dependencies of the differential cross-section and of the Isgur–Wise form factor as functions of the variable w=vB0·vD* have also been obtained by unfolding the experimental resolution.  相似文献   

11.
Rabi oscillations were observed in the ASR(110), ΔM = 0 and ASQ(222), ΔM = 0 transitions of the ν2 band of 14NH3 in a molecular beam crossed by a CO2 laser beam. The frequency (in terms of the laser field amplitude) of the oscillations was used to determine the transition dipole moment of the ν2 band, yielding μsa = 0.261 ± 0.006 D. The hyperfine structure due to the electric quadrupole interaction of the nitrogen nucleus was clearly resolved.  相似文献   

12.
The transient thiophosphenous fluoride FPS was produced by pyrolysis of 2.5% F2PSPF2 in Ar at 1300–1800°C. High-resolution (≥0.004 cm−1) Fourier transform infrared spectra of the a-type ν1 and b-type ν2 bands, centered respectively at 803.249 and 726.268 cm−1, were measured and fitted to rotational and quartic centrifugal distortion parameters. The millimeter-wave spectrum, essentially b-type, was measured between 300 and 370 GHz in the ground state and in the ν3 excited state for FP32S and in the ground state for FP34S. The frequencies were fitted to a Watson-type A-reduced Hamiltonian up to sextic distortion terms. High level ab initio calculations with large basis sets were performed on FPS and supported the first identification of its infrared and millimeter wave spectra. The calculated anharmonic force field provided precise ab initio rovibrational α constants which were combined with the experimental molecular parameters to determine an accurate equilibrium structure of the molecule: re(PS)=188.86 pm, re(PF)=158.70 pm, θ(FPS)=109.28°. The collision-controlled 1/e lifetime measured in a 10-Pa (1 : 20) F2PSPF2/Ar mixture was 2 s, more than two orders of magnitude larger than that of FPO under the same experimental conditions.  相似文献   

13.
Ro-vibrational spectra of HNCS and DNCS have been obtained in the spectral range 300–4000 cm−1 with a practical resolution limit of 0.06 cm−1 in the region 350–1200 cm−1 and 0.15 cm−1 in the region 1200–4000 cm−1. The observed fine structure permitted definitive assignments for some of the PQK, QQK, and RQK branches in both molecules, and yielded sets of rotational constants in substantial agreement with those obtained from recent microwave and far-infrared studies. Precise estimates of the band origins have been obtained and there is evidence of second-order Coriolis coupling between the three bending modes in each molecule. The isolation of the out-of-plane bending modes has lead to a re-assignment of ν3, ν4, ν5, and ν6 for each molecule. The band origins, uncorrected for Coriolis interaction, are for HNCS and DNCS, respectively. v1:3538.6 ±0.3, 2644.5±0.5cm−1;v2:1989.0 ±0.3, 1944.3±0.5cm−1;v3:857.0 ±0.6, 851.0±0.1cm−1;v4:615.0 ±0.5, 549.1±0.2cm−1;v5:469.2 ±0.1, 365.8 ±0.2cm−1;v6:539.2 ±0.5, 481.0±0.1cm−1;  相似文献   

14.
A search for νμ → νe oscillations has been conducted at the Los Alamos Meson Physics Facility (LAMPF) using νμ from π+ decay in flight. An excess in the number of beam-related events from the νe Ce X inclusive reaction is observed. The excess is too large to be explained by normal νe contamination in the beam at a confidence level greater than 99%. If interpreted as an oscillation signal, the observed oscillation probability of (2.6 ± 1.3 ± 0.5) × 10−3 is consistent with the previously reported oscillation evidence from LSND.  相似文献   

15.
The overtone band 2ν08 of CH3CN around 720 cm−1 has been measured on a Bruker Fourier transform spectrometer at a resolution of 0.003 cm−1. Only the parallel band was observed, but due to the l(2, 2) resonance, ΔK = −2 lines leading to the v8 = 2, l8 = −2 levels with K = 1-3 could be seen. More information for the l8 = ±2 component of the vibrational state v8 = 2 was evaluated from the hot band 2ν±28 - ν±18. Altogether more than 1000 lines were assigned. In the fit pure rotational lines from literature were also combined. Among the results the anomalous A0 - A′ values 4.6722(13) × 10−3 cm−1 for the 2ν08 band and 7.0324(32) × 10−3 cm−1 for the 2ν±28 band are striking.  相似文献   

16.
The diffusion ot Ti atoms in the Ni77Si3B20 metallic glass was studied by the Auger electron spectroscopy. The temperature dependence of the diffusion coefficient obeys the Arrhenius relation with the activation energyE=1·7 eV and the pre-exponential factorD 0=0·86 × ×10–4 m2 s–1. Possible mechanisms of the atomic transport in metallic glasses are discussedThe authors wish to thank Dr. P. Duhaj for providing the metallic glass samples.  相似文献   

17.
The 2ν3 overtone (A1E) and the ν1 + ν3 (E) combination bands of the oblate symmetric top 14NF3 were studied by FTIR spectroscopy with a resolution of 2.5 × 10−3 cm−1. Nearly 500 lines up to Kmax/Jmax = 30/43 were observed for the weak A1 component reaching the v3 = 20 substate (1803.1302 cm−1), the majority of which corresponded to reinforced K = 3p-type transitions. For the strong E component reaching the v3 = 2±2 substate (1810.4239 cm−1), about 3550 transitions were assigned up to Kmax/Jmax = 65/69, favoring a clear observation of the ℓ(4, −2) and ℓ(4, 4) splittings within the kℓ = −2 and +4 sublevels, respectively. The two v3 = 2 substates are linked by the ℓ(2, 2)- and ℓ(2, −1)-type interactions, providing severe crossings, respectively, at K′ = 6 and near K′ = 24 on the v3 = 2+2 side. A model working in the D-reduction and including all these ℓ-type interactions could reproduce together 3695 nonzero weighted experimental data (NZW) through 33 free parameters with a standard deviation of σ = 0.357 × 10−3  cm−1. As for the ν1 + ν3 (E) combination band, about 3690 lines were assigned up to Kmax/Jmax = 45/55. Its v1 = v3 = 1 upper state (1931.577 5 cm−1) was treated using the same model recently applied to the v3 = 1 (E, 907.5413 cm−1) state. It yielded 21 free parameters through 3282 NZW experimental data, adjusted with σ = 0.344 × 10−3  cm−1 in the D-reduction. For the two excited states, the small and unobserved ℓ(0, 6) interaction was tested as useless. To confirm the adequacy of the vibrationally isolated models used, some other reductions of the Hamiltonian were tried. For the v3 = 2 state, the D-, L-, and LD-reductions led to similar σ’s, while the Q one was not successful. For the v1 = v3 = 1 state, the D- and Q-reductions gave comparable σ’s, while the QD-reduction was not as good. The corresponding unitary equivalence relations are generally more nicely fulfilled for the v3 = 2 state than for the v1 = v3 = 1 state. The three derivable anharmonicity constants in cm−1 are x33 = −4.1528, g33 = +1.8235 and x13 = −7.9652.  相似文献   

18.
The vibration-rotation spectrum of methyl isocyanide (CH3NC) has been recorded with the aid of a high-resolution Fourier transform spectrometer in the region 1370 to 1560 cm−1 containing the perpendicular band of the fundamental vibration ν6 (species E), the weaker parallel band of the ν3 (A1) fundamental, and the perpendicular combination band ν7 + ν8 (E) enhanced by Fermi resonance with ν6. Sixteen hundred seventy well-resolved lines were assigned to 15 subbands of ν6, 6 subbands of ν3, and 3 subbands of ν7 + ν8. A strong x, y-Coriolis resonance between ν3 and ν6 and Fermi resonance between ν±6 and the E component ν7 + ν8, as well as between ν3 and the A1,2 components ν±7 + ν8, greatly affects the spectrum. Additional weaker anharmonic interaction of ν6 with the ν4 + 2ν28 combination and higher-order rotational interactions connecting the various states were also detected in the spectrum. All of these interactions have been incorporated into a 9 × 9 Hamiltonian matrix used for modeling the upper states of the observed transitions. A set of spectroscopic constants is reported for the upper states of the bands ν3, ν6, and ν7 + ν8 and for ν4 + 2ν28 which reproduces the observed lines with an overall standard deviation of 0.0012 cm−1.  相似文献   

19.
Volume and grain boundary diffusion of 113Sn in aluminium was investigated with the radiotracer method. The implantation technique was used for tracer deposition to avoid problems of tracer hold-up caused by the oxide layer always present on aluminium. The diffusion penetration was chosen large enough to permit serial sectioning of samples with the aid of a microtome.The temperature dependence of the volume diffusivity was determined as D(T)=4.54×10–5×exp[–(114.5±1.2)kJmol–1/RT] m 2 s –1. This confirms previous measurements from our group which already showed that Sn is the fastest foreign metal diffusor so far investigated in aluminium.Grain boundary diffusion of 113Sn in Al polycrystals was measured in the type-B kinetic regime. The grain boundary diffusion product P=sD gb (s=segregation factor, =grain boundary width, D gb=grain boundary diffusivity) was found to be strongly affected by the impurity content of aluminium. For Al polycrystals of 99.9992% nominal purity we obtained P 5N(T)=1.08×10–8exp [–(96.9±7.5) kJ mol–1/RT] m3 s–1 and for less pure Al polycrystals of 99.99% nominal purity P 4N(T)=3.0×10–10 exp [–(90.1±4.2) kJ mol–1/RT] m3 s–1 was determined. The grain boundary diffusion product in the purer material is more than one order of magnitude higher than in the less pure material. Very likely this is an effect of co-segregation of non-diffusant impurities into the grain boundaries.  相似文献   

20.
Using a high-resolution Fourier transform spectrum of hydrogen selenide in natural abundance, about 600 intensities of lines belonging to the ν1, ν3, and 2ν2 bands of H280Se were measured. A least-squares fit of these intensities was performed, allowing determination of the vibrational transition moments of these bands and their rotational corrections. Finally, the first derivatives of the dipole moment with respect to the normal coordinates q1 and q3 were found to be ∂μχ/∂q1 = (−0.5938 ± 0.010) × 10−1 and ∂μz/∂q3 = (0.5683 ± 0.010) × 10−1 Debye, respectively.  相似文献   

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