Kinetic measurements of NCl(a 1 ∆) metastables produced by the photolysis of chlorine azide (ClN 3 ) at 193 nm are reported. High NCl(a 1 ∆) density (>10 15 molecules/cm 3 ) production facilitates measurements of the NCl(a 1 ∆) + NCl(a 1 ∆) self-annihilation rate. A gas phase transient chemical titration scheme is used to calibrate absolute NCl(a 1 ∆) density. The NCl(a 1 ∆) bimolecular rate coefficient at room temperature is (7.2 ( 0.9 × 10 -12 cm 3 /(molecule s) and has a magnitude very critical to the development of an NCl(a 1 ∆) + I( 2 P 3/2 ) f I*( 2 P 1/2 ) + NCl(X 3 Σ -) chemical laser. Despite the large value of the self-annihilation rate, intense I*( 2 P 1/2 ) emission via transfer from NCl(a 1 ∆) is strongly observed when mixtures of CH 2 I 2 and ClN 3 are photolyzed at 193 nm. Unlike the analogous O 2 (a 1 ∆) + I( 2 P 3/2 ) energy transfer system, the relatively large NCl(a 1 ∆) bimolecular rate constant suggests that NCl(a 1 ∆) transport times must be short and will require small chemical mixing regions for efficient lasing. In addition, the 300 K collisional quenching rate constants of NCl(a 1 ∆) by F 2 , Cl 2 , and Br 2 are (2.5 ( 1.1) × 10 -13 , (2.9 ( 0.6) × 10 -11 , and (1.4 ( 0.2) × 10 -10 cm 3 /(molecule s), respectively.

Results of the temperature and infrared wavelength (0.8, 1.4, and 1.9 μm) dependence of terahertz radiation generated from both undoped and Te-doped InSb irradiated with ≊125 fs laser pulses are reported. Undoped InSb shows a substantial change in the spectral content of the terahertz radiation between 80 and 260 K, while the spectrum of Te-doped InSb remains nearly unchanged, an effect attributed to its mobility being dominated by impurity scattering. Also, the terahertz radiation from undoped InSb at 80 K is dependent on the irradiating wavelength, with both a higher frequency spectrum and much larger amplitude generated at longer wavelengths. No such effect is observed at 260 K.

Interaction of vacuum ultraviolet excimer laser radiation with fused silica. I. Positive ion emissionThe infrared emission spectra from 0.9 to 1.651lm produced when thallium iodide vapor is photodissociated by excimer laser wavelengths of 193,248,308, and 351 nm are reported. In this spectral region, only atomic thallium transitions were observed. No emission from metastable atomic iodine at 1.3151lm (5 2 PI12 -+ 5 2 P 312 ) or thallium at 1.2831lm (6 2P3/2 -+6 2P1/ 2 ) was ever detected in contrast to strong 1.3151lm signals obtained by ultraviolet (UV) excimer laser dissociation of C 3 F71. The failure to detect metastable atomic emission from TIl photodissociation is explained by the fast quenching of the metastable states during superelastic collision with electrons produced by photoionization of the TIL Consequently, a pulsed iodine 1.3151lm laser based on photodissociation of thallium iodide does not seem practical.

A tenfold mass production scale-up that provides an economical synthesis method for producing normal-heptafluoropropyl iodide (n-C3F7I) laser ‘‘fuel’’ sustaining stable and reliable cw atomic iodine lasing at 1.315 μ via UV photolysis is reported. Such results strongly indicate that high purity n-C3F7I is being synthesized. Over 1 kg per day production of this n-C3F7I is demonstrated. The synthesis procedure involves three steps: formation of the n-C3F7COONa salt, refluxing at 45 °C, and a packed column distillation. During the synthesis, particular attention is given to minimizing those impurities producing detrimental effects on atomic iodine lasers. Yields of 65%–75% for n-C3F7I laser ‘‘fuel’’ are achieved whenever liquid nitrogen is used to collect the synthesized product.

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