D. Papousek

Vibration-rotational interactions in the states v2 = 1 and v5 = 1 of H312CF

Abstract The vibration-rotational bands ν2 and ν5 of gaseous fluoromethane H312CF have been measured in the region 1250–1600 cm−1 with resolution 0.0034 cm−1; the 2046 lines that have been assigned include 85 lines of the Δk = ±2 perturbation-allowed transitions to the doubly degenerate vibrational state v5 = 1. A variational approach has been applied to the analysis of both bands which are strongly perturbed by x-y Coriolis interaction and by “2, −1” l-type coupling. Simultaneously with 96 previously reported frequencies of pure rotational transitions in the ground vibrational state and 202 frequencies in the excited vibrational states v2 = 1 and v5 = 1 [Pracna, Papousek, Belov, Tretyakov, and Sarka, J. Mol. Spectrosc. 146, 120–126 (1991)], the wavenumbers of 2046 vibration-rotational transitions of the bands ν2 and ν5 have been fitted to determine 7 parameters of the ν2 band and 21 parameters of the ν5 band. The ground state parameters A0 = 5.1820107(12) cm−1 and D K 0 10 −6 = 70.39(15) cm −1 are in excellent agreement with those determined previously [Graner, Mol. Phys. 31, 1833–1843 (1976)]. A standard deviation of 8.0 × 10−4 cm−1 has been obtained in the simultaneous fit of the infrared data and 0.38 MHz of the rotational frequencies of the upper state, but in the ν5 band inexplicable systematic differences up to 0.02 cm−1 between the experimental and calculated wavenumbers remain for certain values of the rotational quantum number K at J > 25. From the analysis of the absolute intensities of lines of the ν2 and ν5 bands, we found that (∂μ x ∂q 5a )/( ∂μ z ∂q 2 ) = +1.75 , which indicates a negative perturbation of intensity (ζ2.5ay

The direct l-type resonance spectrum of CF35 3Cl in its vibrational state v 6 = 1

Using the technique of Fourier transform microwave spectroscopy about 100 direct l-type resonance transitions for CF35 3Cl in the first excited state of the doubly degenerate vibration v 6 have been observed in the range of 2–18 GHz. These transitions are observable due to a mixing of states with Δl = Δk = ±2 by the l-type (2, 2) interaction. In addition to the (2, 2) interaction it was necessary to include two further off-diagonal contributions to explain the spectrum: the (2, -4) interaction, which contributes to the splittings of the transitions with G = |k - l| = 3, and either the (2, -1) or the (0, 3) interaction corresponding to two different reductions of the effective Hamiltonian. The unitary equivalence of both sets of parameters has been demonstrated. The transitions show hyperfine splittings owing to quadrupole rotation-vibration interactions. In a simple approach the theory of Aliev and Hougen has been applied to explain the hyperfine structure patterns and to determine the (2, 2) quadrupole l...

Electric dipole moment derivatives for PH3, PD3, CH3F, CD3F, CH3Cl, and CD3Cl computed by the density functional method

Abstract The first and second derivatives of the electric dipole moments along the symmetry coordinates were computed for PH3, PD3, CH3F, CD3F, CH3Cl, and CD3Cl by means of the deMon density functional program [A. St-Amant and D. R. Salahub, Chem. Phys. Lett.169, 387–392 (1990)]. The results agree well with the available experimental data.

Theoretical vibrational and rotational energies and intensities of the HNSi and DNSi molecules

Using the demon density functional program, 104 points on the potential‐energy surface for the ground electronic state of the HNSi molecule were calculated. An analytic function was fitted through these points and used in two different computer programs (called Morse oscillator–rigid bender internal dynamics and triatom) to calculate the vibration–rotational energies of the HNSi and DNSi molecules. Other analytic functions were fitted through the calculated dipole‐moment data to compute the vibrational transition moments and the vibrationally averaged dipole moments. The computed fundamentals ν1, ν2, and ν3 for HNSi from the triatom program are 3466, 413, and 1172 cm−1, respectively, in reasonable agreement with the observed values of 3588, 523, and 1198 cm−1. Agreement is similar for the Morse oscillator–rigid bender internal dynamics program as well as for DNSi.

Far-infrared spectrum of 13CH3F between 23 and 84 cm−1

Abstract The Fourier transform spectrum of the pure rotational transitions in the ground vibrational state of 13CH3F was measured at an unapodized resolution 0.0019 cm−1 in the 23–84 cm−1 spectrum region at elevated temperature 360 K. 527 lines with J ≤ 50 have been assigned and fitted simultaneously with the previously measured microwave and submillimeter-wave rotational transitions, and combination differences generated from the ν3 band [Papousek, Tesař, Pracna, Kauppinen, Belov, and Tretyakov, J. Mol. Spectrosc., 146, 127–134 (1991)]. Improved set of spectroscopic parameters was obtained for the ground state of 13CH3F except for the sextic coefficient HJ0, which is not determinable even from data with J ≤ 50.

High-resolution Fourier-transform infrared spectrum of the13CH3F fundamental band of13CH3F

Thev6 vibration-rotational band of13CH3F has been measured in the range 1070–1260 cm−1 using a Fourier-transform spectrometer with unapodized resolution 0.0027 cm−1. The wavenumbers of 1262 vibration-rotational transitions to thev6=1 (E) vibrational state have been assigned and fitted by least squares with the standard deviation of the fit 1.31×10−4 cm−1. This made it possible to determine 19 spectroscopical parameters of thev6=1 state including parameters of the Δk=±2, Δl=∓2 and Δk=±4, Δl=∓2 interactions leading to theA1−A2 splittings of many rotational levels withkl=+1 andkl=−2.