Knowledge Bank

During our extensive studies on the spectra of $H3+$ and $CH3+$ using He-dominated AC plasmas, we noted that high rotational levels with $j\cong k$ are anomalously populated. For example, the transition of $H3+$ is clearly observed in spite of the high rotational energy ($>5500$ K), The intensity of the signal is orders of magnitude higher than that expected from thermal equilibrium with the usual rotational temperature of $-500\circ K$, White similar metastability has been reported for interstellar $NH3$ and has been well $understood,1$ observing the same effect in laboratory plasmas is unexpected. A summary of the observed results will be presented.