Thea 3 Σ g + -c 3 Π u andc 3 Π u -a 3 Σ g + systems in the infrared spectrum of H2 and D2
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The infrared H2 laser lines recently discovered by McK night and Barr belong to thea 3 Σ g + -c 3 Π u system. This system has not previously been observed although both upper and lower state are well defined from the visible spectrum. We have observed for H2 both thea≠c and thec≠a transition near 2700 and 2100 cm−1 and for D2 thea≠c transition near 2000 cm−1. Laser action occurs only for the strongest lines of theP branch, viz.P(2) for H2,P(1) for D2 of thea≠c system. The inverted population causing laser action is produced by the strong predissociation of the3 Π u + component of thec state. In thec≠a system the same predissociation causes the absence ofP andR branches. The Δv=0 sequence of thea≠c system lies in the region 100 to 1000 cm−1; it has not been observed. Considering the much larger Franck—Condon factors for this sequence it should give rise to strong laser action.
KeywordsInfrared Spectrum Lower State Visible Spectrum Laser Action Vertical Arrow
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