Development of a tuneable laser source in the vacuum ultraviolet and its applications to spectroscopy
Date
2008-12
Authors
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Journal ISSN
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Publisher
Stellenbosch : Stellenbosch University
Abstract
Third harmonic generation (THG) in a metal vapour is a nonlinear optical
interaction that facilitates the generation of light in the vacuum ultraviolet
(VUV) portion of the electromagnetic spectrum. The requirement of the metal
vapour medium is that it has a suitably large third order nonlinear susceptibility.
The third order susceptibility is further enhanced by a two photon resonance.
Zinc and magnesium vapours are such nonlinear media. The THG process can
be phase matched by mixing the metal vapour with a noble gas in a speci c
pressure ratio. The metal vapour noble gas mixture needs to be homogeneous
and its temperature needs to be constant to within less than a degree Celsius
over a path length of 7 cm. These requirements are satis ed by a crossed heat
pipe oven. The heat pipe oven makes use of a dynamic liquid-vapour phase
equilibrium in sodium in order to maintain a constant temperature of around
800 degrees Celsius, thus facilitating the generation of a stable homogeneous
medium of metal vapour and noble gas that can be used for e cient generation
of VUV radiation. The development of such a VUV source using zinc vapour and
the application of a similar VUV source using magnesium vapour are discussed.
The VUV radiation has been applied to laser induced uorescence spectroscopy
of carbon monoxide (12C16O and 13C16O). Spectral lines of 20 spin-forbidden
singlet-triplet transitions of the e3 − − X1 +(5 0) band were detected and
accurate experimental wavelengths determined for the rst time for ve of these
lines.
Description
Thesis (MSc (Physics))--Stellenbosch University, 2008.
Keywords
Nonlinear four wave sum mixing spectroscopy, Dissertations -- Physics, Theses -- Physics