## Abstract

The depolarisation of selected OH (X^{2}?_{3/2}v = 0, J = 1.5 and 4.5, e) levels in collisions with the molecular partners N_{2} and O_{2} at room temperature (nominally 298 K) has been studied using the polarisation spectroscopy (PS) technique. We obtain total depolarisation rate constants, k^{(K)}_{PS}, which are the combination of population transfer out of the initial level and elastic depolarisation of the tensor moment of respective rank K = 1 (orientation) or K = 2 (alignment) of its angular momentum distribution. N_{2} causes more rapid decay of PS signals than O_{2}. There are no clear dependences of k ^{(K)}_{PS} on J for either partner. The K-dependence for N _{2} mirrors that determined previously for the noble gases, but is less regular for O_{2}, warranting further investigation. Comparison with independent line-broadening data suggests that there may be an additional, pure-elastic-dephasing contribution to collisional broadening for N_{2} that is not apparent for O_{2}. The presence of an independently established deeper HO-OO attractive minimum at shorter range clearly does not outweigh other factors that favour k^{(K)}_{PS} for N _{2}.The most obvious explanation is stronger, longer-range attractive interactions due to the larger quadrupole moment of N_{2}. However, this appears to be contradicted by the rigorous ab initio calculations currently available on OH-O_{2}. © the Owner Societies 2009.

Original language | English |
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Pages (from-to) | 8813-8820 |

Number of pages | 8 |

Journal | Physical Chemistry Chemical Physics |

Volume | 11 |

Issue number | 39 |

DOIs | |

Publication status | Published - 2009 |