Structure and predissociation of the 3pσᵤD³Σᵤ⁺ Rydberg state of N₂: first extreme-ultraviolet and new near-infrared observations, with coupled-channels analysis

Abstract

The 3pσᵤD³Σᵤ⁺ Rydberg state of N₂ is studied experimentally using two high-resolution spectroscopic techniques. First, the forbidden D³Σᵤ⁺-X¹Σg⁺ transition is observed for the first time via the (0,0) band of ¹⁴N₂ and the (1,0) band of ¹⁵N₂, using 1 extreme-ultraviolet +1 ultraviolet two-photon-ionization laser spectroscopy. Second, the Rydberg-Rydberg transition D³Σᵤ⁺-E³Σg⁺ is studied using near-infrared diode-laser photoabsorption spectroscopy, thus extending the previous measurements of Kanamori et al. [J. Chem. Phys. 95, 80 (1991)], to higher transition energies, and thereby revealing the (2,2) and (3,3) bands. The combined results show that the D(v=0-3) levels exhibit rapidly increasing rotational predissociation as v increases, spanning nearly four orders of magnitude. The D-state level structure and rotational predissociation signature are explained by means of a coupled-channels model which considers the electrostatically coupled ³Πᵤ Rydberg-valence manifold, together with a pure-precession L-uncoupling rotational interaction between the 3pσᵤD³Σᵤ⁺ and 3pπᵤG³Πᵤ Rydberg p-complex components.