Intramolecular quantum chaos in doped helium nanodroplets

A mass spectrometric depletion spectrum (17 700–18 300 cm−1) is reported for NO2 in superfluid (0.37 K) helium nanodroplets. Gas phase NO2 is believed to be vibronically chaotic at these energies. Transitions are broadened and blue-shifted relative to their gas phase counterparts. The spectrum is fitted reasonably well by setting all of the widths and shifts equal to 7 cm−1. Modest dispersions (i.e., 90% lie within 2 cm−1 of the central values) are consistent with quantum chaos in NO2. Relaxation is dominated by interactions of NO2 with its non-superfluid helium nearest neighbors.