Time-of-flight scattering measurements at 8.65 eV (c.m.) display strong inelastic scattering from
He(23S)+He(11S) to
He(23P)+He(11S). Close-coupled quantum-mechanical calculations employing ab initio potential curves and matrix elements show the inelastic process is due to strong rotational coupling between the $c ^{3}\ensuremath{\Sigma}_{g}^{+}$ state of
He(23S)+He(11S) and the $b ^{3}\ensuremath{\Pi}_{g}$ state of
He(23P)+He(11S). Good agreement is found between the calculated and the experimentally measured inelastic-scattering cross sections.
We theoretically study inelastic collisions between NO radicals and He atoms at low collision energies, focusing on the occurrence of scattering resonances. We specifically investigate de-excitation of rotationally excited NO radicals (X (2)Π1/2, v = 0, j = 3/2, f) at collision energies ranging from 10(-3) to 20 cm(-1) and compute integral and differential cross sections using quantum mechanical close-coupling calculations. Although unconventional, we show that the measurement of rotational de-excitation cross sections brings several advantages to experiments that aim to study rotational energy transfer at temperatures approaching zero kelvin. We analyze the nature and partial wave composition of the quasi-bound states associated with each individual resonance and compute the scattering wave functions. The differential cross sections contain the partial wave fingerprints of the scattering process and are found to change drastically as the collision energy is varied over the resonances. The prospects for measuring these differential cross sections in inelastic de-excitation collisions at low energies are discussed.
We carry out quantum inelastic scattering calculations of collisions of Rb atoms with inverting
NH3 and
ND3 molecules in the energy range between 0 and $100\text{ }{\text{cm}}^{\ensuremath{-}1}$, which are important for experiments using velocity-controlled molecular beams to probe scattering resonances. We focus on molecules initially in the upper level of the ammonia inversion doublet for
j=1,
k=1, which is low-field seeking and can be controlled in a Stark decelerator. We calculate the integral elastic and state-to-state inelastic cross sections in the coupled-states approximation. We demonstrate the presence of both shape and Feshbach resonances in the elastic and inelastic cross sections at low collision energies and discuss their origin in terms of the bound states of the Rb-
ND3 complex. We also consider elastic and inelastic cross sections in the ultracold regime, using close-coupling calculations, in order to assess the viability of sympathetic cooling of
ND3 by Rb. The inelastic cross section for relaxation to the lower level of the inversion doublet is smaller than expected for such a strongly coupled system but is still likely to be too large to allow sympathetic cooling for
ND3 in low-field-seeking states. However, there is a good prospect that sympathetic cooling will be possible for molecules in high-field-seeking states even when the collision partner is a magnetically trapped atom in a low-field-seeking state.