Emission spectra of group IV monohalide ions: , 3Π1–X1Σ+ emissions of SiBr+

Abstract

Emission spectra of SiBr4 in the rare gas flowing afterglows have been measured to detect and identify SiBr+ emissions. Two systems of SiBr+ emissions were detected in the He, Ne, and Ar afterglows in the region from 335 to 380 nm. By analogy with the emission spectrum of SiCl+, they were ascribed to the [Formula: see text]–X1Σ+ and a3Π1–X1Σ+ subsystems of SiBr+. The vibrational analysis of the latter system gave the following molecular constants for the a3Π1 state: T0 = 29 140 ± 5 cm−1 and ΔG(1/2) = 392.0 ± 3.7 cm−1. The SiBr+ emissions disappeared when ionic species were removed from the afterglows, indicating that the emitting SiBr+ states were produced through thermal-energy reactions of rare gas ions with SiBr4. In the He and Ne afterglows, the [Formula: see text] ions were produced in higher vibrational levels than in the Ar afterglow. The relative vibrational populations in the He and Ne afterglows were nearly exponential with an effective vibrational temperature of 460 ± 30 K.