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Proceedings Paper

Two-Colour Multiphoton Excitation Of Methanol Induced By A CO[sub]2[/sub] And HF Laser
Author(s): Michael Ivanco; D K Evans; Robert D McAlpine
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Paper Abstract

Multiphoton, two-laser absorption by methanol (Pressure = .4 kPa) has been studied photoacoustically. The P1(6) (3694 cm -1) and P1(7) (3644 cm-1) lines, of an HF laser were used together with three C02 laser lines, 10P(20) (944 cm-1), lUR(16) (973 cm-1) and 9P(20 (1047 cm-1). The two lasers were overlapped spatially, with counterpropagating beam geometry, and temporally with a relative jitter of approximately ± 70 ns. Preliminary results show that when the HF laser pulse (w1) precedes the CO2 laser pulse (ω2), with ωl exciting the molecule into the quasicontinuum (QC), there was a two-colour enhancement (TCE) of the multiphoton absorption signal which was considerably red-shifted from the C-0 stretch fundamental absorption maximum. The maximum enhancement observed was for the lUR(16) line which is approximately 60 cm-1 to the red of the C-0 stretch absorption maximum. There was also a significant two-colour absorption observed for the 10P(20) line at moderate CO2 laser fluences (50 J/cm'), whereas there is no one colour signal observed for this line at fluences as high as 100 J/cm4. No TCE was observed when the CO2 laser (9P(20) line) preceded the HF laser pulse and pumped the molecule into the QC, for either the P1 (6) or P1 (7) HF laser lines. In addition, no dependence of TCE on CO2 laser pulse intensity was observed when using 10 ns as compared to 60 ns pulses. There is noc enough data, at this point, to say whether there are several regions of varying absorption intensity in the OC or whether there is only one broad red-shifted peak, hot experiments along these lines are continuing.

Paper Details

Date Published: 25 November 1986
PDF: 6 pages
Proc. SPIE 0669, Laser Applications in Chemistry, (25 November 1986); doi: 10.1117/12.938933
Show Author Affiliations
Michael Ivanco, Chalk River Nuclear Laboratories (Canada)
D K Evans, Chalk River Nuclear Laboratories (Canada)
Robert D McAlpine, Chalk River Nuclear Laboratories (Canada)

Published in SPIE Proceedings Vol. 0669:
Laser Applications in Chemistry
D. K. Evans, Editor(s)

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