Abstrakt
We present studies on the thermalisation of H-3(+) ions in a cold He/Ar/H-2 plasma at temperatures 30-70 K. We show that we are able to generate a rotationally thermalised H-3(+) ensemble with a population of rotational and nuclear spin states corresponding to a particular ion translational temperature.
By varying the para-H-2 fraction used in the experiment we are able to produce para-H-3(+) ions with fractional populations higher than those corresponding to thermodynamic values. At 35 K, only the lowest rotational states of para and ortho H-3(+) are populated.
This is the first step towards experimental studies of electron-molecular ion recombination processes with precisely specified quantum states at astrophysically relevant temperatures.