Joe J. Tiee

Optically pumped molecular lasers in the 11–17‐μm region

A large number of laser transitions in the 11–17‐μm region have been obtained by optically pumping CF4, NOCl, CF3I, and NH3 with a single line‐tunable CO2 TEA laser. These lasers have respectable conversion efficiency and can be scaled to high energies in a spectral region where the selective excitation of molecules is prerequisite to performing selective photodissociation and laser‐induced chemistry experiments.

CF4 and NOCl molecular lasers operating in the 16‐μm region

We have obtained stimulated emission in the 16‐μm egion from CF4 and NOCl with an optical pumping scheme which uses a single CO2 TEA laser as the excitation source. Measured laser energies from CF4 and NOCl are 4 and 3 mJ, respectively, which represents an order‐of‐magnitude improvement over exisiting molecular lasers oscillating in this region. There appear to be no fundamental limitations to scaling these lasers to energies ⩾1 J. These lasers offer considerable promise for the laser isotope separation of uranium.

The photodissociation of UF6 using infrared lasers

Abstract The ir collisionless multiple photon absorption (cmpa) photodissociation of UF 6 is reported. Single frequency photodissociation is a accomplished with the focused output from a pulsed CF 4 laser operating at 615 cm -1 . When focusing the CF 4 laser output with a 7.5 cm f.1. lens, photodissociation is observed at laser energies as low as 5 mJ. By using a CO 2 laser (0.7 J, 1077 cm -1 ) in concert with the CF 4 laser, significant enhancement (factors of 10–100) of the photodissociation yield is obtained at low CF 4 laser energies. Electronic emission is observed from the focal region, but only when both lasers are present.

Transient molecular absorptions induced by the absorption of CO2 laser radiation

Abstract Laser-induced molecular absorptions are reported for the species SF 6 , CF 3 I, and CF 3 Br. Induced absorptions are observed at frequencies ∼ 40 cm -1 lower than that of a CO 2 TEA laser which is used to vibrationally excite the molecules in a low pressure cell. The dependence of the effect on pump laser intensity indicates that the species that exhibit the induced absorption have absorbed more than one laser photon. Applications of this phenomenon with respect to laser induced isotope separation are discussed.

ir photolysis of SeF6: Isotope separation and dissociation enhancement using NH3 and CO2 lasers

The isotopically selective ir photodissociation of SeF6 using two lasers is reported. The output from an NH3 laser (780.5 cm−1, 0.75 J, 0.5 μsec FWHM) and a line tunable CO2 TEA laser (2.5 J, 150 nsec FWHM) are combined in order to enhance the photodissociation rate. Although the CO2 laser output by itself is ineffective in dissociating SeF6, the CO2 laser output can enhance the NH3 laser photolysis of SeF6 by as much as a factor of 50. We find that the isotopic selectivity is independent of the CO2 laser energy, and the rate of dissociation is unaffected by changing the CO2 laser frequency.

High‐energy optically pumped molecular lasers in the 13‐ and 16‐μm regions

This paper describes the construction of an optically pumped laser device. The device utilizes a line‐tunable CO2 TEA laser as a source to optically pump a cell which is capable of cooling candidate laser gases down to ∼150 °K. Laser outputs of 750 mJ in the 13‐μm region and 100 mJ in the 16‐μm region are obtained by pumping NH3 and CF4 respectively with 10 J of CO2 laser radiation. The measured conversion efficiencies are 15% for NH3 and 3% for CF4. These lasers can be used to photodissociate polyatomic molecules and are attractive sources for practical laser isotope separation.

Isotopically selective ir photodissociation of SeF6

The isotopically selective ir photodissociation of SeF6 is reported. The output from an NH3 laser (780.5 cm−1, 50 mJ, 200 nsec FWHM) is used to photodissociate SeF6, and the five abundant isotopes of Se are all enriched despite the rather small (∼1.6 cm−1/amu) isotope shift of the ν3 vibration. These results are predictable using a simple empirical technique which can be applied equally well to the ir photodissociation of other molecules.

Optically pumped NSF molecular laser

An optically pumped NSF laser, with tunable output in the region 618–658 cm−1, and pumped with a tunable transversely excited atmosphere (TEA) CO2 laser, is described. This laser promises to be an attractive source for laser isotope separation.

High-energy pulsed CO chemical laser

A high‐energy pulsed CO chemical laser has been constructed. Vibrationally excited CO molecules are produced via the reaction O+CS→CO†+S. A laser output of 240 mJ/pulse is obtained when a mixture of CS2 and O2 is flash photolyzed without any additives. When small amounts of N2O and O3 are introduced, an output energy of 360 mJ/pulse is obtained.