Collisional depolarization of OH(A) studied by Zeeman quantum beat spectroscopy

M. Brouard; A. Bryant; I. Burak; S. Marinakis; F. Quadrini; I. Anton Garcia; C. Vallance

doi:10.1080/00268970500096293

Collisional depolarization of OH(A) studied by Zeeman quantum beat spectroscopy

M. Brouard^*, A. Bryant, I. Burak, S. Marinakis, F. Quadrini, I. Anton Garcia, C. Vallance

^*Corresponding author for this work

University of Oxford

Research output: Contribution to journal › Article › peer-review

31 Scopus citations

Abstract

The depolarization of the rotational angular momentum of electronically excited OH(²Sigma;) radicals through collisions with water molecules has been measured using Zeeman quantum beat spectroscopy. The new data have permitted the evaluation of OH(A) state-specific quenching and angular momentum depolarization cross-sections for superthermal OH(A) radicals with mean relative velocities centred around 3500 m s^-1. The quenching cross-sections are compared both with values available in the literature, and with predictions based on a simple harpoon model, and are found to be in good qualitative accord with previous findings. For the lowest rotational levels studied, the depolarization cross-sections (which include contributions from both elastic and inelastic processes in OH(A)) are found to approach ∼100 Å², only slightly below the high-temperature cross-sections for rotational energy transfer determined elsewhere. The data suggest that under the present conditions rotational energy transfer is accompanied by significant depolarization. The cross-section for the translational moderation of superthermal OH(X) by water is also determined in the present study.

Original language	English
Pages (from-to)	1693-1702
Number of pages	10
Journal	Molecular Physics
Volume	103
Issue number	13
DOIs	https://doi.org/10.1080/00268970500096293
State	Published - 10 Jul 2005
Externally published	Yes

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@article{e18bafd738e24e4a9808b5fda5598e33,

title = "Collisional depolarization of OH(A) studied by Zeeman quantum beat spectroscopy",

abstract = "The depolarization of the rotational angular momentum of electronically excited OH(2Sigma;) radicals through collisions with water molecules has been measured using Zeeman quantum beat spectroscopy. The new data have permitted the evaluation of OH(A) state-specific quenching and angular momentum depolarization cross-sections for superthermal OH(A) radicals with mean relative velocities centred around 3500 m s-1. The quenching cross-sections are compared both with values available in the literature, and with predictions based on a simple harpoon model, and are found to be in good qualitative accord with previous findings. For the lowest rotational levels studied, the depolarization cross-sections (which include contributions from both elastic and inelastic processes in OH(A)) are found to approach ∼100 {\AA}2, only slightly below the high-temperature cross-sections for rotational energy transfer determined elsewhere. The data suggest that under the present conditions rotational energy transfer is accompanied by significant depolarization. The cross-section for the translational moderation of superthermal OH(X) by water is also determined in the present study.",

author = "M. Brouard and A. Bryant and I. Burak and S. Marinakis and F. Quadrini and {Anton Garcia}, I. and C. Vallance",

note = "Funding Information: The support from EPSRC (to MB) and SSF (to SM) are gratefully acknowledged. It is also a pleasure to acknowledge helpful discussions regarding weak fields with Dr Christiane Timmel (PTCL, Oxford) and similar discussions about the Faraday rotation technique with Oleg Vasyutinskii (Ioffe Institute, St Petersburg). CV also gratefully acknowledges the support of the Royal Society.",

year = "2005",

month = jul,

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doi = "10.1080/00268970500096293",

language = "אנגלית",

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T1 - Collisional depolarization of OH(A) studied by Zeeman quantum beat spectroscopy

AU - Brouard, M.

AU - Bryant, A.

AU - Burak, I.

AU - Marinakis, S.

AU - Quadrini, F.

AU - Anton Garcia, I.

AU - Vallance, C.

N1 - Funding Information: The support from EPSRC (to MB) and SSF (to SM) are gratefully acknowledged. It is also a pleasure to acknowledge helpful discussions regarding weak fields with Dr Christiane Timmel (PTCL, Oxford) and similar discussions about the Faraday rotation technique with Oleg Vasyutinskii (Ioffe Institute, St Petersburg). CV also gratefully acknowledges the support of the Royal Society.

PY - 2005/7/10

Y1 - 2005/7/10

N2 - The depolarization of the rotational angular momentum of electronically excited OH(2Sigma;) radicals through collisions with water molecules has been measured using Zeeman quantum beat spectroscopy. The new data have permitted the evaluation of OH(A) state-specific quenching and angular momentum depolarization cross-sections for superthermal OH(A) radicals with mean relative velocities centred around 3500 m s-1. The quenching cross-sections are compared both with values available in the literature, and with predictions based on a simple harpoon model, and are found to be in good qualitative accord with previous findings. For the lowest rotational levels studied, the depolarization cross-sections (which include contributions from both elastic and inelastic processes in OH(A)) are found to approach ∼100 Å2, only slightly below the high-temperature cross-sections for rotational energy transfer determined elsewhere. The data suggest that under the present conditions rotational energy transfer is accompanied by significant depolarization. The cross-section for the translational moderation of superthermal OH(X) by water is also determined in the present study.

AB - The depolarization of the rotational angular momentum of electronically excited OH(2Sigma;) radicals through collisions with water molecules has been measured using Zeeman quantum beat spectroscopy. The new data have permitted the evaluation of OH(A) state-specific quenching and angular momentum depolarization cross-sections for superthermal OH(A) radicals with mean relative velocities centred around 3500 m s-1. The quenching cross-sections are compared both with values available in the literature, and with predictions based on a simple harpoon model, and are found to be in good qualitative accord with previous findings. For the lowest rotational levels studied, the depolarization cross-sections (which include contributions from both elastic and inelastic processes in OH(A)) are found to approach ∼100 Å2, only slightly below the high-temperature cross-sections for rotational energy transfer determined elsewhere. The data suggest that under the present conditions rotational energy transfer is accompanied by significant depolarization. The cross-section for the translational moderation of superthermal OH(X) by water is also determined in the present study.

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JO - Molecular Physics

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Collisional depolarization of OH(A) studied by Zeeman quantum beat spectroscopy

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