The 313 nm band system of SeO2. Part 1: vibrational structure

A part of the 313 nm band system of SeO2 near its origin has been recorded in the gas phase by laser-excitation spectroscopy. The spectrum was recorded with a sample containing the various isotopes of selenium in their natural abundance. The vapour was formed by heating the solid to 320 degreesC and then cooled in a free-jet expansion. The spectrum obtained is consequently much better resolved than any recorded previously. The vibrational assignments made by King and McLean [J. Mol. Spectrosc. 51 (1974) 363] have been largely confirmed. Some corrections, notably of the v band, and some extensions of the vibrational assignments have allowed the determination of the vibrational parameters for the symmetric stretching (v(1)) and bending (v(2)) vibrations for both the upper (C) over tilde B-1(2) and lower (X) over tilde (1)A(1) electronic states. The first vibrational intervals obtained are as follows: v(1)', = 626.0 cm(-1). v(2)' = 265.3 cm(-1) v(1) = 920.8 cm(-1). v(2)(n) = 369.8(5) cm(-1) each with all uncertainty of 0.5 cm(-1). No convincing evidence is found to support the Suggestion by King and McLean that SeO2 has a double-minimum potential in the antisymmetric stretching vibration q(3) in the (C) over tilde B-1(2) state. (C) 2004 Elsevier Inc. All rights reserved.