Linked Life Data

19757776

Source:http://linkedlifedata.com/resource/pubmed/id/19757776

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PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
52
pubmed:dateCreated
2009-12-23
pubmed:abstractText
Two color polarization spectroscopy has been employed to measure the collisional depolarization of OH(A(2)Sigma(+), v = 1) by He and Ar. Complementary experiments using Zeeman quantum beat spectroscopy have also been performed to determine separately the cross sections for rotational energy transfer (RET) out of selected rotational levels of OH(A, v = 0) + Ar, as well as those for elastic depolarization. This has been achieved by dispersing the emission, so as to observe a single fluorescence transition. Elastic depolarization of OH(A) by Ar is found to be significant with that for loss of rotational alignment exceeding that for loss of orientation. In the case of OH(A) + He, the polarization spectroscopy measurements suggest that elastic depolarization plays a relatively minor role in the loss of the polarization signal compared with RET. The experimental data for OH(A) + Ar are compared in detail with the results of quasi-classical trajectory calculations that accommodate the effects of electron spin. These classical calculations are assessed against the results obtained using full close-coupled open shell quantum mechanical scattering methods. Overall the level of agreement between the two experiments, and between experiment and theory, is very reasonable. Surprisingly, at low N the elastic depolarization cross sections for OH(A) + Ar are found to be quite similar in magnitude to those observed for OH(X) + Ar despite the fact that the well depth in the latter system is considerably smaller than that for OH(A)-Ar. However, for OH(A) + Ar the depolarization cross sections are insensitive to N in the range 1-14. It is proposed that this behavior partly reflects the relatively anisotropic nature of the potential energy surface, which exhibits deep wells of different depths at the two linear configurations OH(A)-Ar and Ar-OH(A), and partly the nature of elastic depolarizing collisions, which must occur with a velocity component perpendicular to the plane of rotation of the diatomic molecule.
pubmed:language
eng
pubmed:journal
pubmed:status
PubMed-not-MEDLINE
pubmed:month
Dec
pubmed:issn
1520-5215
pubmed:author
pubmed:issnType
Electronic
pubmed:day
31
pubmed:volume
113
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
15156-70
pubmed:year
2009
pubmed:articleTitle
Elastic depolarization of OH(A) by He and Ar: a comparative study.
pubmed:affiliation
School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, United Kingdom.
pubmed:publicationType
Journal Article