Knowledge Bank

The v-20-17 band of the $HD\ast$ molecular ion has been observed using a sequential two-photon photodissociation technique. The experiments were performed by Doppler - tuning a fast beam of $HD\ast$ into resonance with the fixed frequency of a collinear carbon dioxide laser beam. Doppler limited linewidths of about 5 MHz were achieved, permitting the partial resolution of the hyperfine structure. The two lowest dissociation limits of $HD\ast ,H++D(ls)$ and $H(1s)+D+$, are separated by about $30cm-1$, the former being the lower limit. For very high vibrational levels, such as v=20 which lies about $100cm-1$ below the $H++D(ls)$ limit, the electron density about the deuteron is expected to be higher than about the proton. This suggestion is confirmed by simulations of the hyperfine structure for transitions of the 20-17 band.