High-resolution laser spectroscopy and photodissociation dynamics of OH⁺

Abstract

The paper reports high-resolution spectra of the c¹Π–b¹Σ⁺ and c¹Π–a¹Δ electronic transitions of OH⁺ obtained by detecting O and O⁺ photofragments, which arise from predissociation of the c¹Π electronic state. Five vibrational bands of the c¹Π–b¹Σ⁺ system and three of the c¹Π–a¹Δ system of ¹⁶OH⁺ were recorded and molecular parameters derived from the analysis. Spectra of the ¹⁶OD⁺ isotopic modification were also taken. A study of perturbations between the A³Π and b¹Σ⁺ states leads to improved determination of the spin–orbit interaction between these states and their relative energies. A selective predissociation mechanism operates with laser excitation to ¹Π (e) levels strongly weighted towards formation of O + H⁺, whereas ¹Π (f) levels yield O⁺ + H exclusively. The predissociation decay rates are also dependent on the c ¹Π state vibrational and rotational quantum numbers. The measured linewidths for v′ = 2 and 3 are in good agreement with both a theoretical approach based on spectroscopic parameters and the results of high-quality ab initio calculations of Yarkony.