2+1 resonance-enhanced multiphoton ionisation spectroscopy of the high ν2 levels of the B̃1E″ Rydberg state of NH3(ND3)

State-to-state resolved differential cross sections for rotationally inelastic scattering of ND3with He

“…10 Cheung et al 11 noted that the 35 observed NH 3 emission intensities from interstellar sources do not correspond to a single rotational temperature. In addition, the inversion transition was detected for the rotational level j k = 11 9 , 12 which should not be populated at interstellar temperatures of 10-300 K, and the j k = 3 3 inversion transition has been predicted 13 40 and observed 14 to exhibit maser activity. These observations clearly showed that the emitting NH 3 is not in thermal equilibrium with its environment.…”

“…[39][40][41] One consequence of symmetry and nuclear spin constraints is that only transitions originating from the lower (+) inversion component of the ground state appear in bands in which the final ߥ ଶ is even, whereas only transitions from the upper (−) inversion 35 component appear in bands with final ߥ ଶ odd. Therefore, two vibrational transitions must be excited to probe all individual rotational states.…”

“…Therefore, two vibrational transitions must be excited to probe all individual rotational states. The ‫ܤ‬ ෨ ሺߥ ଶ ൌ 4ሻ ՚ ܺ ෨ ሺߥ ଶ ൌ 0ሻ transition at wavelengths near 321 nm probes ND 3 states with + inversion symmetry populated by the scattering, while -inversion 40 symmetry of the final scattering states is probed by the ‫ܤ‬ ෨ ሺߥ ଶ ൌ 5ሻ ՚ ܺ ෨ ሺߥ ଶ ൌ 0ሻ transition at wavelengths around 317 nm. Figure 3 shows the rotational REMPI spectra of non-scattered ND 3 molecules in the primary beam, measured with and without hexapole state selection, for 2-photon excitation via the ߥ ଶ = 4 45 and 5 vibrational levels of the ‫ܤ‬ ෨ state.…”

“…Although there is a significant body of work on inelastic scattering of diatomic molecules, such detailed experimental and computational investigations for scattering of polyatomic molecules remain relatively rare. 26 40 A number of PESs have been developed previously for the NH 3 -He 2, 27-32 scattering system. In addition, theoretical DCSs for this system were reported by Meyer et al 29 state approximation and by van der Sanden et al coupling methods with empirical and scaled 45 energy surfaces.…”

“…The expanding Newton sphere of ND 3 + ions prepared by REMPI of scattered ND 3 was extracted by static electric fields toward the VMI detector, which consisted of a pair of position sensitive microchannel plates (MCPs) located in front of a 40 phosphor screen viewed by a CCD camera synchronized with the UV laser pulses. The laser also created ions with other masses, so the detector was switched on only for a short period of time to detect only those ions with the desired mass-to-charge ratio.…”