Indirect predissociation of highly excited singlet states of N2

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 1Πu 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 1Πu and o3 1Πu Rydberg states. This leads to the dissociation of b′(20) into the continuum of the b 1Πu valence state. The residual observed predissociation of b′ 1Σu+(v = 20) apart from the rotationally-localised peak cannot be explained by a mechanism of 1Πu and 1Σu+ interaction, and must involve states of higher multiplicity