Rotational analysis of the SiD2 Ã 1B1–X̃ 1A1 transition observed in a jet

Abstract

The SiD2 radical was produced by ArF laser photolysis of C6H5SiD3 in a free-jet expansion, and the laser-induced fluorescence (LIF) excitation spectrum of the à 1B1–X̃ 1A1 transition of SiD2 was measured. The LIF excitation spectra of the five vibronic bands, (0,v2′,0)–(0,v2″,0), v2′–v2″= 0–0, 1–0, 2–0, 1–1, and 2–2, were obtained using a narrow-band dye laser with an intracavity étalon, the resolution of which attained to ∼0.03 cm−1. The rotational structures of the vibronic bands were well analyzed by a Hamiltonian including fourth-order terms, and the molecular constants were determined for the vibronic levels, v2=0, 1, and 2, of the à 1B1 and X̃ 1A1 states. By comparing the observed rotational line intensities with simulated ones, we found two kinds of intensity anomalies depending on the rotational quantum numbers J and Ka. We conclude that both the anomalies are caused by a predissociation process to the dissociation continuum, Si(3P)+D2, which was proposed in our previous paper [J. Chem Phys. 96, 44 (1992)]. The Ka dependent anomaly was explained by the interaction terms in the Fermi Golden Rule expression for the predissociation process, and the J dependence was interpreted by the final-state density.