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1.
The rotational constants of the B 1 state of indium iodide are reported for the first time as Be = 0.037533 cm−1 and αe = 0.000289 cm−1 while Te = 25050.60 cm−1 for the B1-X0+ transition. Accurate vibrational constants are also computed from measured Q heads as ωe= 146.36 cm−1 and ωeχe = 2.20 cm−1.  相似文献   

2.
The near-edge structure of the Ti K-edge absorption spectra was calculated for BaTiO3, SrTiO3, and CaTiO3 crystals by the full multiple scattering method. The results obtained are in agreement with the experimental data. The numerical experiment revealed the mechanisms forming the structure of the main edge of the spectra. Original Russian Text ? N.M. Novikovskii, E.S. Nazarenko, A.A. Novakovich, R.V. Vedrinskii, 2008, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2008, Vol. 72, No. 4, pp. 462–464.  相似文献   

3.
We report new measurements of the 5 ← 4 through 9 ← 8 lines in the pure rotational spectrum of nitrous oxide, 15N15N16O, and measurements at room temperature and at an elevated temperature of the 1000-0000 and 020-0000 bands of that molecule. The new data together with data for 10 other vibration-rotational transitions which previously have been reported enable us to determine the ground state constants. Using the newly determined values of B000, D000, and H000, we have determined the band origins and the upper state constant differences B - B000, D - D000, and H - H000 of 25 vibration-rotational bands whose lower level is the ground vibrational state.  相似文献   

4.
The geometry, complete harmonic force field, and dipole moment derivatives of cubane, C8H8, have been calculated at the Hartree-Fock level using a 4–21 Gaussian basis set. The infrared and Raman spectra of cubane and four deuterated derivatives were calculated and compared with previously observed spectra. A set of five scale factors for the calculated force constants was then derived by least-squares fitting of the fundamental vibrational frequencies calculated from the scaled force field to the frequencies obtained by direct experimental measurement. The resulting scaled quantum-mechanical (SQM) force field, containing 73 unique elements, is believed to give an accurate representation of the harmonic vibrational potential of cubane. In most cases, the spectral assignments previously made from purely empirical considerations were confirmed, but a few corrections are proposed. The only major alteration is for an A2u mode revised to appear at 1030 cm?1 in the undeuterated molecule. Coriolis constants and approximate infrared intensities are also calculated.  相似文献   

5.
6.
The 333.6-, 351.1-, and 363.8-nm lines of a cw argon ion laser are found to coincide with the BaS B1Σ+-X1Σ+ (12, 0) R(17), (6, 0) P(35), and (3, 0) R(125) transitions, respectively. Fluorescence transitions from the laser-prepared upper levels terminating in X1Σ+ V = 0–28, A1Σ+ V = 1–3, A1Π V = 1–13, and a3Π1 V = 3–12 are assigned. These results are combined with a previous analysis of the extensively perturbed BaS A1Σ+-X1Σ+ system [R. F. Barrow, W. G. Burton, and P. A. Jones, Trans. Farad. Soc.67, 902–906 (1971)]. Every observed perturbation of the BaS A1Σ+ state is electronically and vibrationally assigned. The levels a3Π0 V = 10–13, a3Π1 V = 12–14, a3Π2 V = 15, and A1Π V = 10–13 are sampled via their perturbations of A1Σ+ V = 0–2. Although the mutual interactions of the a3Π, A1Π, and A1Σ+ states approach Hund's case (c) limit, a complete deperturbation is performed from a case (a) starting point. Of the five lowest energy electronic states of BaS, only b3Σ+ remains uncharacterized. Principal deperturbed molecular constants are (in cm−1, 1σ uncertainties in parentheses):
  相似文献   

7.
We have developed a flexible and thoroughly tested computer program for microscopic calculations of proton-induced pion production in nuclei at bombarding energies up to 500 MeV. The model used includes explicitly both the one-nucleon (pionic stripping) mechanism and the resonant p-wave rescattering part of the two-nucleon mechanism. Initial and final state interactions are included through proton-nucleus and pion-nucleus optical model distortions, with careful consideration of the multiple scattering series. The intermediate delta in the two-nucleon mechanism is treated as static with possible inclusion of a local density approximation for the delta-nucleus interaction. We explain the philosophy of the model, detail the parametrization of the microscopic dynamics, and give the formalism for the calculation of experimental observables. We also describe the testing of the computer program and present preliminary results for the 3He(p, π+)4He reaction.  相似文献   

8.
A variational procedure for rovibrational energy levels and wavefunctions of centrally connected tetra-atomic molecules is extended to include high rotational states, and in particular, J ? 10 levels for the vibrational ground state of formaldehyde. It is very important to do this because it has made possible the calculation of the usual rotational spectroscopic constants which correspond to the forcefield and geometry. A direct comparison with the ‘observed’ spectroscopic constants is therefore possible. The geometry and forcefield are refined against 65 J = 0 levels of H2CO, 6 J = 0 levels of D2CO, 42 J = 1, 70 J = 2 and 98 J = 3 levels of the ground and fundamentals of H2CO and D2CO, using an iterative scheme. The mean absolute error of the J = 0 levels is 1·10 cm?1 and that for J ≠ 0 is 0·005 cm?1, and the predicted geometry is CH = 1·10064 Å, CO = 1·20296 Å and HCO = 121·648°. Finally, the rotational constants A, B, and C for the ground state are 281956, 38846 and 34003 MHz, compared with the observed values 281971, 38836, and 34002 MHz. The centrifugal distortion constants ΔJ , ΔJK , ΔK and δJ , are 77, 1275, 18113 and 11 kHz compared with 75, 1291, 19422 and 10 kHz. These results underline the accuracy of the new quartic forcefield.  相似文献   

9.
A time-resolved experiment on the A2Π state of gaseous calcium hydride has been performed by applying laser spectroscopic methods. The following zero-pressure lifetime was obtained for the CaH A2Π state: τυ´=0 = 33.2 (±3.2) ns and τυ´=1 = 33.7 (±5.2) ns. The lifetime was found to be the same for the A2Π½ and A2Π3/2 states.  相似文献   

10.
We have measured the deuteron A(Q2) structure function in the momentum transfer region between 1 and 18 fm−2. The accuracy of the data ranges from 2 to 6%. These measurements allow a sensitive test of theoretical predictions. We find that meson-exchange currents and relativistic corrections significantly improve the agreement between experiment and theory. We investigate the sensitivity of A(Q2) to the nucleon-nucleon interaction and to the neutron electric form factor GEn(Q2). Our analysis shows that GEn(Q2) can be extracted from these data with a significantly improved accuracy. The model dependence of this analysis is discussed.  相似文献   

11.
12.
A reinvestigation of the A0+-X10+ band system, the most electronic transitions reported for bismuth monofluoride, is presented. Approximately 65 bands were photographed in emission between 4220 and 5417 Å, of which 33 were rotationally analyzed. Inconsistencies in earlier vibrational analyses were resolved. Rotational constants for 0 ≤ ν′ ≤ 12 and 0 ≤ ν″ ≤ 18 were determined from direct least-squares fitting to the measured line positions of each band. “Merging” of the overdetermined constants was performed to obtain the best single estimate of each parameter. The resulting minimum-variance linear unbiased estimates were used to calculate RKR potential curves. Franck-Condon factors and r centroids were subsequently obtained and are presented. Evidence is given for predissociation in the upper state; perturbations involving levels above the crossing point are correlated with those previously reported in the B0+ state. The upper limit of the ground-state dissociation energy (3.14 eV) is in accord with extrapolated values as given in earlier investigations. The nature of a postulated third interacting state is also discussed.  相似文献   

13.
14.
The J = 2?1 microwave spectrum of six isotopic species of HSiF3 has been observed and assigned in excited states of five of the six fundamental vibrations. The assignment is based on relative intensities, double resonance experiments, and trial anharmonic force constant calculations. Analysis of the spectra leads to experimental values for five of the αrB constants, all three l-doubling constants qt, one Fermi resonance constant φ233, and one zeta constant ζ6, 6(z).The harmonic force field has been refined to all the available data on vibration wavenumbers, centrifugal distortion constants, and zeta constants. The cubic anharmonic force field has been refined to the data on αrB and qt constants, using two models: a valence force model with two cubic force constants for SiH and SiF stretching, and a more sophisticated model. With the help of these calculations, the following equilibrium structure has been determined: re(SiH) = 1.4468(±5) A?, re(SiF) = 1.5624(±1) A?, ∠HSiF = 110.64(±3)°,  相似文献   

15.
Theoretical values of vibrational frequencies and rotational constants for all the isotopomers of nitrous oxide are reported. The calculations are carried out variationally using an empirical Morse-cosine potential energy surface previously determined for N2O, and a set of optimal internal vibrational coordinates. The spectroscopic constants obtained are compared to those extracted from spectroscopic measurements for the , , , , , and isotopomers. The agreement between calculated and observed values for these isotopomers is shown to be excellent, especially for the rotational constants. As a result, an unidentified band recently recorded is properly assigned. The spectroscopic constants computed for the rest of the isotopomers, for which observed information is much scarcer, have therefore a predictive character. The vibrational zero point energies for all the N2O isotopomers are also given.  相似文献   

16.
Potential energy and dipole moment surfaces of the 1A′ ground state of HeScH2+ have been calculated using both the internally contracted single and double excitation multireference configuration interaction and the coupled-cluster singles and doubles augmented by a perturbative treatment of triple excitations levels of theory. Analytical functions have been fitted to the discrete surfaces employing a multidimensional least squares approach. These analytical functions have subsequently been embedded within a rectilinear normal-coordinate vibrational Hamiltonian in order to calculate vibrational states and transition intensities for low-lying states of HeScH2+.  相似文献   

17.
Fairly strong, regularly spaced absorption lines have been observed in the microwave spectrum of HNCS and assigned to b-type, Ka = 0 ← 1, Q-branch transitions arising from molecules in the lowest excited vibrational state. The Fortrat diagram of these lines has the appearance of a c-type Q branch, which is impossible in HNCS because of its symmetry. This anomalous b-type Q-branch spectrum is caused by strong a-type Coriolis interactions among the three low-lying bending modes; the Ka = 1 levels of the lowest excited vibrational state are perturbed and shifted lower in energy than the Ka = 0 levels for each J. This interpretation has been confirmed by the observation of P- and R-branch transitions associated with this Q branch. The band origin has been determined to be ?40 104.287 MHz (?1.3377 cm?1). The inversion of the Ka = 0 and 1 energy levels is consistent with the interpretation of HNCS as a quasi-linear molecule.  相似文献   

18.
In the microwave and millimeter wave spectra of HNCO, the b-type transitions between the Ka = 0 and 1 levels in the lowest excited vibrational state have been observed. Because of strong a-type Coriolis resonances among the three bending excited states the energy difference between the levels for Ka = 0 and 1 is much smaller in the lowest excited state than in the ground state. The subband origin of these b-type transitions has been found in the millimeter wave region at 275 697.309 MHz (9.1963 cm?1). The effect of the Coriolis resonances is discussed in relation to the molecular quasi-linearity and is compared with the case of HNCS.  相似文献   

19.
20.
An analysis of the ν6=1 state of fluoroform is performed using rotational and high resolution infrared spectra. Previously radiofrequency data [Chem. Phys. Lett. 214 (1993) 265–270] and millimeter data [J. Mol. Spectrosc. 131 (1988) 1–8] were combined with new millimeter and infrared measurements, and a set of 27 parameters has been derived. A multiple fit analysis was performed confirming the assumption that the ν6=1 excited state is not affected by intervibrational resonances.  相似文献   

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