Spectroscopy Of Triatomic Hydrogen .1. Bands Near 5600-A, 5800-A And 6025-A

The visible emission spectra of H3, D2H, H2D and D3 were studied. Triatomic hydrogen molecules were produced by neutralization of fast ion beams in alkali vapors. In addition to the well-known 0-0 bands, weak vibrational bands of the electronic 3p2A?2 ? 2s2A'1 transition of D3 and D2H were observed and analyzed. From the decay of the emission along the molecular beam lifetimes of excited states were obtained. For all observed states, 3p2A?2, 3s2A'1 and 3d, lifetimes strongly depend on the isotopic mixture. Many lifetimes measured were considerably shorter than ab initio predictions of the radiative lifetimes. Thus radiationless decay is important for all these excited states. Predissociation of the 3p2A?2 state increases with the rotational quantum number. Possible decay channels are discussed.