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Fluorescence polarization effect in ultrafast rotational anisotropy measurements
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
1999 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 103, no 16, 2912-2916 p.Article in journal (Refereed) Published
Abstract [en]

Unidirectional signal detection in time-resolved rotational anisotropy experiments has been known to affect the time zero and time infinity (persistent alignment) values because these measurements can overestimate the parallel or perpendicular components of the signal. Here we demonstrate that the well-known expression for obtaining the rotational anisotropy, a quantity that is typically calculated to measure the alignment, rotational energy, or rotational constants of molecules, is not applicable for some of the most common experimental configurations. We report new formulations that take into account different unidirectional detection schemes and the f-number of the collection optics. Femtosecond time-resolved anisotropy measurements on iodine vapor were obtained, with typical right-angle detection, to illustrate how the new expression corresponding to this configuration yields the expected time zero and time infinity values. Fits to the observed anisotropy are shown to provide quantitatively accurate results.

Place, publisher, year, edition, pages
American Chemical Society , 1999. Vol. 103, no 16, 2912-2916 p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:su:diva-24811DOI: 10.1021/jp9845064OAI: oai:DiVA.org:su-24811DiVA: diva2:198346
Note
Part of urn:nbn:se:su:diva-7462Available from: 2008-04-09 Created: 2008-03-28 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Quantum Wavepacket Dynamics in Molecular and Trapped Ion Systems
Open this publication in new window or tab >>Quantum Wavepacket Dynamics in Molecular and Trapped Ion Systems
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The motions of a wavepacket in the two coupled potentials studied in this thesis can be classified into either bistable or astable motion according to the wavepacket interference at the curve crossing. Bistable motion, in which the wavepacket performs a coupled oscillation but remains in the same adiabatic and diabatic state, can exist both in bound-bound systems and bound-unbound ones with long time stability. Astable motion, in which the wavepacket at the curve crossing switches between the adiabatic and diabatic states and thus alternates between the two possible turning points in the unforked part of the motion, can only exist in bound-bound systems on a limited time scale. The motion of a wavepacket under bistable interference conditions exhibits all of the features expected if the wavepacket moved in a single anharmonic potential. The revival time can be predicted from the revival times in the corresponding diabatic and adiabatic potentials. The phenomenon was observed not only in model molecular systems but also in the system of the harmonically trapped ion pumped by an external laser field with standing wave spatial profile.

In order to study the bias effect of the detector on pump-probe rotational anisotropy measurements, in a specific direction the fluorescence polarization effect was removed by measuring the rovibrational wavepacket with the help of properly oriented polarizer placed in front of the detector. Our results show clearly the necessity to take polarization effects into account in ultrafast pump-probe rotational anisotropy measurements.

Place, publisher, year, edition, pages
Stockholm: Fysikum, 2008. 84 p.
Keyword
wavepacket, revival, anisotropy, polarization
National Category
Atom and Molecular Physics and Optics
Research subject
Chemical Physics
Identifiers
urn:nbn:se:su:diva-7462 (URN)978-91-7155-625-7 (ISBN)
Public defence
2008-04-30, sal FB52, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:30
Opponent
Supervisors
Available from: 2008-04-09 Created: 2008-03-28Bibliographically approved

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