Tunable Far-Infrared Spectroscopy of HF, H35Cl, and H37Cl in the 6 to 9 THz Region

Analysis of rotational and vibrational-rotational spectra of HF based on the non-Born-Oppenheimer effective Hamiltonian

Rotational transitions of HF that are important as a wavenumber standard have been analyzed by simultaneous fitting of the reported rotational and vibrational-rotational transitions plus rotational measurements of the present study with the non-Born-Oppenheimer effective Hamiltonian expressed with the optimal parameters, i.e., the determinable clusters of the expansion coefficients of the correction functions for the breakdown of the Born-Oppenheimer approximation. Since the spectral fit is made with the analytical solution of the Schrödinger equation, one can easily reproduce the fitting procedure. This is the first example of the non-Born-Oppenheimer analysis of a single isotopologue with physically meaningful parameters based on the traditional concept of the molecular constants. Fitting of a data set for HF has generated 15 independent parameter values that include 4 determinable clusters of the expansion coefficients. These 15 parameters are sufficient to generate 41 Yij coefficients and 72 rotational constants, which provide comprehensive sets of molecular constants of HF.

The B Σ+ and X 1Σ+ Electronic States of Hydrogen Fluoride: A Direct Potential Fit Analysis

All literature pure rotational and vibration-rotational spectroscopic data on the ground X (1)Sigma(+) electronic state of HF and DF, together with the entire set of spectroscopic line positions from analyses of the B (1)Sigma(+) --> X (1)Sigma(+) emission band systems of HF and DF, have been used in a global least-squares fit to the radial Hamiltonian operators, in compact analytic form, for both electronic states. With a data set consisting of 6157 spectroscopic line positions, the reduced standard deviation of the fit was sigma = 1.028. Sets of quantum mechanically significant rotational and centrifugal distortion constants were calculated for both electronic states using Rayleigh-Schrödinger perturbation theory.

The Radial Hamiltonians for the X(1)Sigma(+) and B(1)Sigma(+) States of HCl

All literature vibration-rotational and pure rotational transition energies for the ground X(1)Sigma(+) electronic state of H(35)Cl, H(37)Cl, D(35)Cl, and D(37)Cl, along with the entire collection of electronic B(1)Sigma(+) --> X(1)Sigma(+) emission data for the four isotopomers, have been used in a least-squares fit of compact analytic Born-Oppenheimer potential functions for the B(1)Sigma(+) and X(1)Sigma(+) electronic states. Additional functions related to the adiabatic and nonadiabatic corrections have also been determined. Separate least-squares fits were made according to the hamiltonian operators of J. K. G. Watson (J. Mol. Spectrosc. 80, 411 (1980)) and R. M. Herman and J. F. Ogilvie (Adv. Chem. Phys. 103, 187 (1998)). The results from the separate analyses demonstrate clearly that the two hamiltonian operators are essentially equivalent, both achieving equally satisfactory representations of the spectral data, and furnishing virtually identical Born-Oppenheimer potential functions. Fully quantum-mechanical vibrational eigenvalues and rotational perturbation series parameters B(v)-O(v) are presented for the lower levels of the X(1)Sigma(+) ground state for which infrared and/or microwave data are available (v" </= 7 for H(35)Cl and H(37)Cl, v" </= 10 for D(35)Cl and D(37)Cl). These parameters collectively reproduce the corresponding spectroscopic line positions included in our fit to within the uncertainties of the measurements. Copyright 2000 Academic Press.