Indirect predissociation of highly excited singlet states of N₂

Abstract

Indirect predissociation of the b′¹Σu⁺(v = 20) level of N₂ is studied experimentally by vacuum-ultraviolet photoabsorption employing synchrotron radiation and a Fourier-transform spectrometer, and interpreted with the aid of a quantitative model of interacting ¹∏u and ¹Σu⁺, bound and unbound states which solves the coupled Schrödinger equation. An observed rotationally-localised peak in the b′(20) predissociation linewidths is identified by the model as arising from an interaction with a strongly predissociated and unobserved bound level of the mixed c₃ ¹∏u and o₃ ¹∏u Rydberg states. This leads to the dissociation of b′(20) into the continuum of the b ¹∏u valence state. The residual observed predissociation of b′ ¹Σu⁺(v = 20) apart from the rotationally-localised peak cannot be explained by a mechanism of ¹∏u and ¹Σu⁺ interaction, and must involve states of higher multiplicity.