Showing papers by "Jonathan Tennyson published in 1984"

On the rovibrational levels of the H3 ÷ and H2D ÷ molecules

Abstract: Variationally exact rovibrational levels for the H3 + and H2D+ molecules are calculated using a recently published accurate potential. Vibrational fundamentals are v A 1 = 3191 cm-1 and vE = 2494 (2521·6) cm-1 for H3 + and v 1 = 3000 cm-1, v 2 = 2184 cm-1 and v 3 = 2310 cm-1 for H2D+. For H3 + calculated ground state rotational constants are B 0 = 43·51 (43·57) cm-1, C 0 = 20·59 (20·71) cm-1, DJ 0 = 0·04 (0·05) cm-1, DJ K 0 = -0·07 (-0·10) cm-1 and DK = 0·04 (0·04) cm-1 (where experimental results are given in parenthesis). An attempt is made to stabilize many vibrational states. We thus reassess the results of Carney and Porter. The implications for astrophysics, the interpretation of the infrared spectrum of H3 + near its dissociation limit and the unassigned spectrum of H2D+ are discussed.

Low-energy e-H2+ collisions using the R-matrix method

Abstract: The R-matrix method is applied to the electronic excitation of the hydrogenic molecular ion by low-energy electron impact using a two-state coupled-channel formalism. Polarisation effects are accounted for by means of an optical potential which involves no arbitrary parameters. These are the first calculations of this type in which both channel coupling and correlation effects are explicitly included. Good agreement is obtained with other computational techniques. New estimates are made of the positions and widths of the two lowest resonances in each of the Sigma and Pi symmetry states. Excitation cross sections Q(1 sigma g,1 sigma u) are also presented.

Ab initio dipole surfaces, vibrationally averaged dipole moments, and infrared transition intensities for KCN and LiCN

Abstract: Using the rovibrational wave functions which have been obtained from ab initio potentials and making analytic fits to the ab initio calculated dipole surfaces, we have evaluated the dipole (transition) moments of KCN and LiCN for several vibrational states (for J=0 and 1). The ‘‘exact’’ rotational transition intensities of the a‐type transitions in (triangular) KCN and those of (linear) LiNC and LiCN can be rather accurately reproduced by a rigid rotor model with the vibrationally averaged dipole moments; for the (weak) b‐type transitions in KCN this model breaks down, however. Although the bending motions in these cyanides have large amplitudes, the vibrational transition intensities in LiNC and LiCN conform to the harmonic oscillator model. In KCN, where the large amplitudes of the bending modes and their coupling with the K–CN stretch leads to significant anharmonic shifts in the transition frequencies, the harmonic intensity pattern is perturbed by Fermi resonances, for instance, between the stretch f...