First, detection of the visible absorption spectrum of H2O+ and D2O+

Abstract

The visible emission spectrum of the water cation, H2O+, is a prominent feature in comet tails, and is often observed in laboratory discharges. However, until now the visible electronic spectrum has never been observed in absorption. We have used a tunable ring dye laser and a velocity-modulated discharge to detect the A ˜ 2 A ˜ 1 − X ˜ 2 B ˜ 1 visible electronic spectrum in absorption, in H2O+ and D2O+.