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"Ultrasensitive Ultraviolet - Visible 20-fs Absorption Spectroscopy of low Vapor Pressure Molecules in the Gas Phase" C. Schriever, S. Lochbrunner, E. Riedle, D. J. NesbittRev. Sci. Instrum. 79, 013107 (2008) Abstract: We describe an ultrasensitive pump probe spectrometer for transient absorption measurements in the gas phase and in solution. The tunable UV pump and the visible (450 – 740 nm) probe pulses are generated by two independently tunable noncollinear optical parametric amplifiers, providing a temporal resolution of 20 fs. A low gain photodetector and a digitizing scheme for single shot analysis of the light pulses at kHz repetition rates are developed that minimize the shot noise and electronic noise contributions to the transient absorption signal. The data processing scheme is optimized to yield best suppression of the laser excess noise and thereby transient absorbance changes down to 1.1×10-6 can be resolved. A collinear focusing geometry optimized for a 50 mm interaction length combined with a heatable gas cell allows us to perform measurements on substances with low vapor pressures, e.g., on medium sized molecules which are crystalline at room temperature. As an application example, highlighting the capability of this instrument, we present the direct time-domain observation of the ultrafast excited state intramolecular proton transfer of 2-(2'-hydroxyphenyl)benzothiazole in the gas phase. We are able to compare the resulting dynamics in the gas phase and in solution with a temporal precision of better than 5 fs. Copyright: Copyright (2008) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Rev.Sci.Instrum. 79, 013107 (2008) and may be found at http://link.aip.org/link/?RSINAK/79/013107/1. BMO authors (in alphabetic order): Stefan Lochbrunner Eberhard Riedle Christian Schriever  PDF-Version WWW-Version |
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Letzte Änderung: 2016-09-14 13:34
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