OBSERVATION AND IDENTIFICATION OF THE G(6)PHI-A(6)DELTA TRANSITION IN THE BLUE SYSTEM OF FEH AT 493-NM

The blue system of FeH, at 493 nm, has been recorded with a sample at near-ambient temperatures by laser excitation spectroscopy. With the help of dispersed fluorescence studies, all the strong lines in this region of the spectrum have been assigned to the (0,0) band of the g (6) Phi-a (6) Delta transition, where the lower state lies about 1890 cm(-1) above the ground (4) Delta state. Assignments have been made to Delta Omega=+1 and Delta Omega=0 subbands involving the lowest three spin components in each state. Term values have been determined for the levels of the three lowest spin components of the a (6) Delta state and thereby for the g (6) Phi(11/2) spin component, which were hitherto unknown. It is established that the a (6) Delta State of FeH is inverted and that the vibrational interval Delta G(1/2) varies markedly between the spin components of this state: [GRAPHICS] There is evidence that the a (6) Delta state is perturbed by levels of other, nearby electronic states and it is not possible to model its levels with a simple effective Hamiltonian. The radiative lifetime of FeH in the two lowest spin components of the g (6) Delta, State has been measured as 39+/-2 ns.