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25 November 1986 Two-Colour Multiphoton Excitation Of Methanol Induced By A CO2 And HF Laser
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Proceedings Volume 0669, Laser Applications in Chemistry; (1986)
Event: 1986 Quebec Symposium, 1986, Quebec City, Canada
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.
© (1986) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Michael Ivanco, D K Evans, and Robert D McAlpine "Two-Colour Multiphoton Excitation Of Methanol Induced By A CO2 And HF Laser", Proc. SPIE 0669, Laser Applications in Chemistry, (25 November 1986);


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