THE EMISSION-SPECTRUM OF HELIUM HYDRIDE .3. BANDS NEAR 5200-A, 5300-A, AND 6000-A

The emission bands of helium hydride near 5200, 5300, and 6000 Å were analyzed for 4HeH and 3HeD. They are assigned to the emission of nine (HeD) or eight (HeH) coupled electronic states to the A 2Σ+ (5200 and 5300 Å) and B 2Π (6000 Å) states. Because of the high rotational temperature of 2500 - 3500 K and several perturbations, a very complex rotational structure was observed. The strongest band near 6000 Å is emitted by the five components of the 3d states, which show strong uncoupling of the 3d electron from the symmetry axis. The D 2Σ+ and 3pE 2Π states interact by A-type doubling interaction and with the 3d states since interactions with Δl = ± 1 are allowed in a strongly polar molecule as HeH. The line intensities are affected by interference effects due to the interactions of the electronic states, by different lifetimes of the upper states and by predissociation, which is only strong for the A′ parity component of 4HeH. © 1990 American Institute of Physics.