Three and two photon absorption spectroscopy:REMPI of HCl and HBr

Ágúst Kvaran*, Huasheng Wang  and Benedikt G. Waage
Science Institute, University of Iceland, Dunhaga 3, 107 Reykjavík, Iceland


 Approximation expressions for absorption linestrengths due to W´= 0,1,2,3 <- W ´´= 0 (S,P,D and F <- S)  transitions for  three-, two- and one- photon absorptions are summarized. Those for three and two photon absorptions are used to analyse room temperature (3+1) and (2+1) REMPI spectra due to transitions to Rydberg states in HCl and HBr to give spectroscopic parameters. A mechanism of the three-photon excitation process for the E(1S+) <- X(1S+), (0,0) transition in HCl is proposed.  A Rydberg state, not observed  in single or two photon absorption, with band origin  80167 cm-1 was identified in (3+1)REMPI of HBr and analysed for the first time. It was assigned as the l(3F(W´=3)) ((s2p3)5dd)) state, (0,0) band. Use of the three photon absorption line strength expressions for deriving rotational population distributions in ground state HBr is demonstrated.

updated: 25th Nov. ´00