Rotational Excitation by Resonant Transfer of Electronic Excitation
Molecular hydrogen is unique among molecules in that its rotational constant or rotational line separation 2B (=0.0147 eV) is at least an order of magnitude larger than the rotational constants for other molecules (2B = 5 × 10-4 eV for N2, for example). This relatively large rotational line separation for H2 raises the possibility that rotational excitation of level J with inelastic threshold 2B(2J+3) can occur at thermal energies by transfer of electronic excitation from, say, hydrogen atoms initially prepared in excited states with moderate and large quantum numbers n(~5–20). In the event that such an energy transfer is resonant, i.e., when the electronic energy released via de-excitation exactly balances that required for the rotational excitation, an extremely large cross section would be evident, particularly at very low temperatures.
KeywordsLarge Cross Section Excitation Cross Section Rotational Excitation Large Quantum Number Incident Molecule
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