Measurement of the visible absorption spectrum of D2O+ by velocity modulation spectroscopy

We have measured the A-X visible system of D2O+ in the (0,10,0)-(O,O,O) band, using a ring dye laser and velocity-modulation spectroscopy. This is the first observation of this spectrum in absorption. This species is important for its prominent Renner-Teller effect. The velocity-modulation technique suppresses the absorption signal from excited neutrals; also, neutral absorbers and ionic absorbers produce different lineshapes. The best previous work in the visible on this species was obtained by Lew and Groleau, using emission spectroscopy of a discharge with a grating monochromator. Our new measurements include a number of previously unmeasured transitions