Knowledge Bank

We have observed microwave transitions in the $HD+$ and $D2+$ ions involving energy levels very close to their dissociation limits. In $HD+$ the spectrum detected arises from a rotational transition between the two highest bound vibration-rotation levels in the 1s6 ground state (v--21 and $v-22)1.D2+$ has seven vibration-rotation levels supported by the van der waals minimum in the first excited $2p\sigma u$ electronic $state2$ and we have detected microwave electronic transitions between these and high-lying vibration-rotation levels of the ground $1s\sigma g$ electronic state.