Perturbations in the multiphoton ionization spectrum of the F 1Δ state of HCl.

The 2+1 REMPI spectra of the F(0–0), F(1–0), E(0–0), and V(11–0) transitions of HCl were measured in a time-of-flight molecular beam machine. Both room temperature HCl, and rotationally and vibrationally excited HCl obtained by photodissociating vinyl chloride at 193 nm, were used. Several anomalies in the F state were observed. These include a decrease in intensity of the P, Q, and R branches between J’=3 and J’=10 for the 0–0 transition, a falloff in intensity for J’>5 for the P, Q, and R branches of the 1–0 transition, and an enhanced intensity loss of the Q(9) line of the 0–0 transition. Accurate values of the lambda-doublet splitting constants for these transitions were also obtained. The intensity loss in the 0–0 transition is due to an interaction with some unobserved bound state, which could also explain the 1–0 perturbation. A candidate for the perturbing state is the e 3Σ+(1). The isolated perturbation of the Q(9), 0–0 line could be caused by an interaction with the g(0+) state. [ABSTRACT FROM AUTHOR]