Formation and Destruction of Para and Ortho H3+ in Discharge and Afterglow. Experiments with Para-Hydrogen
Abstract
In the present work, we investigated the time evolution of the H3+ ion’s concentration in para and ortho states separately in a pulsed microwave discharge (in a He/Ar/H2 gas mixture) and in afterglow plasma. For this purpose, a near infra-red cavity ring-down spectrometer (CRDS) was used.
In the experiments, we observed conversion between both nuclear spin states and production of H3+ in afterglow. We constructed the model of chemical kinetics for discharge and afterglow to explain such production process.
The anomaly in plasma decay was found to be possibly caused by reaction chain initiated by excited argon atoms and ArH+ ions remaining in the beginning of the afterglow. The hydrogen gas concentration seems to be crucial for the speed of establishment of a steady state ratio between para-H3+ and ortho-H3+ in the afterglow.