Rydberg and valence state excitation dynamics: a velocity map imaging study involving the E–V state interaction in HBr

Abstract

Photoexcitation dynamics of the E(¹Σ⁺) (v′ = 0) Rydberg state and the V(¹Σ⁺) (v′) ion-pair vibrational states of HBr are investigated by velocity map imaging (VMI). H⁺ photoions, produced through a number of vibrational and rotational levels of the two states were imaged and kinetic energy release (KER) and angular distributions were extracted from the data. In agreement with previous work, we found the photodissociation channels forming H*(n = 2) + Br(²P_3/2)/Br*(²P_1/2) to be dominant. Autoionization pathways leading to H⁺ + Br(²P_3/2)/Br*(²P_1/2) via either HBr⁺(²Π_3/2) or HBr⁺*(²Π_1/2) formation were also present. The analysis of KER and angular distributions and comparison with rotationally and mass resolved resonance enhanced multiphoton ionization (REMPI) spectra revealed the excitation transition mechanisms and characteristics of states involved as well as the involvement of the E–V state interactions and their v′ and J′ dependence.