ROTATIONAL ANALYSIS AND ASSIGNMENT OF THE GREEN BAND SYSTEM OF FEH TOTHE E-(6)PI-A-(6)DELTA TRANSITION

The technique of laser excitation spectroscopy at Doppler resolution h as been used to record bands in the electronic spectrum of FeH around 532 nm. A number of lines were also recorded at sub-Doppler resolution using intermodulated fluorescence spectroscopy. Dispersed fluorescenc e studies were used extensively to aid the assignment of a total of 15 3 lines in this region of the spectrum to either the (0,0) or the (0,1 ) band of the e (6) Pi-a (6) Delta transition. All the assignments fro m the excitation spectrum obey the selection rule Delta Omega=-1, givi ng subbands which involve the lowest three spin components in each sta te; transitions with Delta Omega=0 were seen only in dispersed fluores cence. Term values have been determined for the three components in bo th the ground vibrational level of the e (6) Pi electronic state and t he first excited vibrational level of the a (6) Delta electronic state (those for the v=0 level of the a (6) Delta State have been determine d previously). This study provides the first characterization of the s pin components and the rotational levels of the e (6) Pi state of FeH. This state is heavily perturbed and exhibits pronounced lambda-type d oubling, making it very difficult to model the energy levels using an effective Hamiltonian approach. (C) 1997 American Institute of Physics .