RESOLUTION OF ANOMALIES IN THE GEOMETRY AND VIBRATIONAL FREQUENCIES OF MONOBROMOSILYLENE (HSIBR) BY PULSED DISCHARGE JET SPECTROSCOPY

A detailed examination of the ground and first excited singlet electro nic states of HSiBr has been carried out through analysis of the 500-4 00 nm band system, using pulsed discharge jet and laser-induced fluore scence techniques. HSiBr and DSiBr have been produced by an electric d ischarge through SiHBr3 and SiDBr3 vapor in argon. Rotational analysis of the 0(0)(0) bands yielded the structural parameters r(0) ''(SiH) = 1.518(1) Angstrom, r(0) ''(SiBr) = 2.237(1) Angstrom, theta(0) '' = 9 3.4(3)degrees, r(0)'(SiH) = 1.497(10) Angstrom, r(0) ''(SiBr) = 2.208( 2) Angstrom, and theta(0)' = 116.4(7)degrees. Previous anomalies in th e geometric parameters and vibrational frequencies have been resolved and the ground state bond lengths and vibrational frequencies are foun d to be comparable to those of SiH and SiBr. Harmonic force fields hav e been determined for the ground and excited states and the radiative Lifetime of HSiBr has been measured to be 598 +/- 18 ns. (C) 1996 Amer ican Institute of Physics.