Observation of the P2 radical by resonance-enhanced multiphoton ionisation spectroscopy

Abstract

Three hitherto unobserved vibrational levels of the b′³Σ^–_u electronic state of P₂ have been identified via the rotationally resolved, one-photon resonance enthancements they provide in the multiphoton ionisation spectrum of this radical. Analysis yields an extended set of spectroscopic constants for the b′³Σ^–_u state and a first estimate of the relative strengths of the parallel and perpendicular contributions to the P₂(b′³Σ^–_u–X ¹Σ⁺_g) transition moment. One additional, particularly intense but unresolved feature observed at an excitation wavelength of ca. 320.75 nm is tentatively assigned in terms of a two-photon resonance involving a Rydberg state of P₂ with ¹Σ⁺_g symmetry.