Anharmonic potential function, geometry, and energy levels of SiH 3

Abstract

An effective potential energy function of the silyl radical SiH 3 was determined by fitting a general analytic expression to the experimental laser diode data of SiH 3 [C. Yamada and E. Hirota, Phys. Rev. Lett. 56, 923–925 (1986)] and to the resonance enhanced multiphoton ionization (REMPI) spectra of SiH 3 and SiD 3 [R. D. Johnson, B. P. Tsai, and J. W. Hudgens, J. Chem. Phys. 9, 3340–3359 (1989)] and by making use of accurate ab initio results calculated in this study supplemented by additional literature data. In order to obtain a numerically stable and physically meaningful solution of the fitting procedure, the inversion potential constants were constrained by adopting the reduced double-minimum potential concept and by keeping several (in-plane) and (in-plane)-(out-of-plane) force constants fixed at their previously determined ab initio values. The actual fitting was performed using a modified version of the nonrigid inverter Hamiltonian approximation [V. S̆pirko, J. Mol. Spectrosc. 101, 30–47 (1983)] in which a variational description of the ( x- y) Coriolis interaction between the ν 2 and ν 4 vibrational modes is introduced. The fitted potential energy function provides roinversional energy levels in excellent agreement with the available experimental data. Present predictions of the unobserved roinversional transitions of the ν 4 ± and ( ν 2 + ν 4) ± vibrational levels are therefore expected to be reliable.