Vibration-rotation spectroscopy of the HD+ion near the dissociation limit

In previous work we have established that the electronic wavefunction for HD+ becomes extremely asymmetric as the lowest dissociation limit, H+ + D(1s), is approached, with the electron tending to become localised at the deuteron. Recent improvements in our experimental techniques have resulted in a 104 increase in sensitivity, and we have now located the 22-17 band in HD+, and remeasured the 21-17 band with greatly improved resolution. The increase in sensitivity has also enabled us to make radiofrequency/infrared double resonance measurements in the 21-17 band. We now present a detailed analysis of the hyperfine structure in these bands, and compare the hyperfine constants derived with the results of new ‘full two state’ calculations.