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Saturation Phenomena in LIF Measurements, Appendix BOptical saturation is the phenomenon in which the laser-induced rates of absorption and spontaneous emission between two levels, induced by a laser, become comparable to or greater than the spontaneous emission and collision rates connecting these levels. This results in the excited state population N(u) acquiring a value of similar magnitude to that of the ground state, N(e). Under these conditions the observed fluorescence signal, which is proportional to N(u), is no longer linearly dependent on laser intensity I, but increases at a slower rate, and in principle ultimately becomes independent of I. A conceptual picture of optical saturation using a two-level picture is described. This is, however, inadequate for the description of a real experiment involving a molecule, such as OH, for several reasons, which will be explained briefly; these are the multi-level nature of the electronic states and energy transfer among them and effects due to spatial, spectral, and temporal fluctuations in the laser pulse.
Document ID
19850006030
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Date Acquired
August 12, 2013
Publication Date
December 1, 1984
Publication Information
Publication: Assessment of Tech. for Measuring Tropospheric H sub x O sub y
Subject Category
Geophysics
Accession Number
85N14339
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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