Multiphoton absorption (MPA) studies of fluoroform-d, a molecule of interest for potential laser based hydrogen isotope separation processes, are reported for CDF3 pressures 0.2–1.3 kPa, and for a variety of 10 μm CO2 laser lines with pulse widths of 2 or 6 ns and fluences within the range 10−3–70 J/cm2. Unlike SF6, no red shift of the MPA spectrum relative to the small signal spectrum was observed at high fluence. Selective multiphoton decomposition (MPD) experiments using the 10R(26) line, 6 ns pulse to excite the CDF3 component in natural-abundance CHF3 (∼ 150 ppm D/H) at a pressure of 13.3 kPa resulted in the recovery of water enriched up to 30% in deuterium—a measured isotope enrichment of ⩾2000 fold. This demonstrates that a product, highly enriched in deuterium, can be recovered from the selective MPD of fluoroform.

A simple and inexpensive microcomputer data-acquisition system is described for the investigation of the absorption of infrared photons using a photoacoustic detector. The system produces a graphic display of the results during an experiment and permits the operator to correct procedural errors.

The multiphoton absorption of CO2 laser 9 μm P(18), P(20) and P(34) lines by methanol has been studied for fluences from 10−3 to ∼ 20 J/cm2, pulse widths of 6 and 60 ns FWHM and methanol pressures from 0.067 to 13.3 kPa. The absorption depends on laser fluence, laser line and gas pressure but not on laser beam intensity. For each line studied the results can be expressed as a function of fluence and the product of pressure with pulse width. Absorption by a Q‐branch transition (9P(34) pumping) shows a faster relaxation and a stronger absorption than R‐branch transitions (9P(18) and 9P(20) pumping). The results obtained here are compared to multiphoton absorption data for an HF laser pumping the OH stretch vibration.

. Can. J. Chem. 62, 1525Chem. 62, (1984. Studies of the multiphoton absorption (MPA) and decomposition (MPD) of cyclobutanone have been extended to short pulses (10 and 40 ns fwhm) and low pressures (0.01 -1.3 kPa) spanning conditions from essentially no gas kinetic collisions during the laser pulse to a collisional regime. MPA results are modelled by a rotational hole-filling model with a system relaxation time of 0.07 (kPa ns)-' and no dependence on laser intensity is observed. By contrast, decomposition appears to be more efficient using a 10 ns pulse than one of 40 ns. Results are reported for both major and minor products and a mechanism for MPD consistent with these results is discussed.

Can. J. Chem. 66, 857 (1988). Multiphoton absorption (MPA) by ethanol has been studied using pulsed HFand C02 lasers. For the same laser fluence, a C02 laser excites the ethanol molecule to a much higher energy than an HF laser. The multiphoton decomposition (MPD) of methanol has been studied using the 9P(16) C02 laser line for pulse widths of 10 and 60 ns. The major decomposition channel produces C2H4 and HZO. However, other decomposition channels, resulting in the products CH3CH0, C2H6, CH4, and C2H2, are also studied and the channel ratios are found to vary with laser pulse width and with pressure. The mechanistic implications of these results are discussed.