Vacuum Ultraviolet Photodissociation Branching Ratios of 12C16O, 13C16O, and 12C18O from 100500 to 102320 cm–1

Abstract

The C⁺ ion photofragment spectra and photodissociation branching ratios into the two energetically available channels, C(¹D) + O(³P) and C(³P) + O(³P), have been obtained for the three CO isotopologues, ¹²C¹⁶O, ¹³C¹⁶O, and ¹²C¹⁸O, in the vacuum ultraviolet range 100500–102320 cm^–1. The two vibronic states of ¹Σ⁺ symmetry, F(3dσ) ¹Σ⁺(υ′ = 1) and J(4sσ) ¹Σ⁺(υ′ = 0), predominantly dissociate into the lowest channel C(³P) + O(³P) through interactions with the repulsive D′¹Σ⁺ state. All three vibronic states of ¹Π symmetry, E′¹Π(υ′ = 1, 2) and G(3dπ) ¹Π(υ′ = 0), dissociate into both of the channels above. The photodissociation branching ratios into the channel C(¹D) + O(³P) for E′¹Π(υ′ = 1, 2) are found to be independent of both the rotational quantum number and e/f parity, while those for G(3dπ) ¹Π(υ′ = 0) strongly depend on the rotational quantum number, indicating very different predissociation pathways between the valence states E′¹Π(υ′ = 1, 2) and the Rydberg state G(3dπ) ¹Π(υ′ = 0). The potential energy curves of CO in the aforementioned energy range and below have recently been well constructed due to a series of interplays between high-resolution spectroscopic studies and theoretical calculations; the photodissociation branching ratios measured in this study can provide further benchmarks for future theoretical investigations which aim to understand the detailed predissociation dynamics of CO.