The origin band of the A 2 Π u -X 2 Π g electronic transition of the linear pentaacetelyne cation, HC 10 H + , and isotopic derivatives, HC 10 D + and DC 10 D + , has been recorded in the gas phase. The absorption spectrum was observed by cavity ring down spectroscopy through a supersonic planar plasma expansion. The spectrum comprises both spin-orbit components with resolved P-and R-branches. Contour fits allow the determination of ground and excited state spectroscopic constants.

Electronic ground-state SrF (X 2 Σ) products formed in the reaction of electronically excited Sr( 3 P 1 ) with HF are studied using laser-induced fluorescence (LIF) detection. Sr atoms are excited to the 3 P 1 state using a frequency-narrowed and -stabilized linear titanium-sapphire laser at 689.3 nm. The vibrational and rotational population distributions in the SrF(X 2 Σ) products are deduced from the LIF spectra of the B 2 Σ-X 2 Σ and A 2 Π 3/2 -X 2 Σ transitions using spectrum simulation. The results show a strong dependence of the SrF internal energy distribution on the impact parameter. The light H atom is ejected with high translational energy.

Stray light in single-monochromator Brewer instruments increases the uncertainty of solar UV spectral irradiance measurements and ozone retrievals. To study how spectral irradiance within and outside the measurement ranges of the instruments affects the stray light, two Brewer MKII instruments were characterized for the level of in-and out-of-range stray light at multiple laser wavelengths. In addition, several solar-blind filters utilized in single-monochromator Brewers to limit out-of-range stray light were characterized for spectral and spatial transmittances. Finally, the measurement results were used to simulate the effect of stray light and stray light correction on the spectral irradiance and ozone measurements at different wavelength regions. The effect of stray light from wavelengths above 340 nm was found to be negligible compared to other sources of uncertainty. On the other hand, contribution from wavelengths between 325 nm and 340 nm can form a significant portion of the overall stray light of the instrument, with 325 nm being the upper limit of the nominal measurement range of the instrument.

An all-solid-state tunable continuous-wave ͑cw͒ laser operating near 272 nm with a bandwidth ⌫ Ϸ3 MHz has been developed. The third harmonic of light from a single-cw Ti:Sapphire laser has been generated using two external enhancement cavities. An output power of 175 mW has been produced, corresponding to an overall conversion efficiency of 8%. © 2003 American Institute of Physics. ͓DOI: 10.1063/1.1584515͔All-solid-state tunable lasers are compact and reliable sources of high-power narrow-band coherent radiation. The applicability of these lasers, however, is limited as they mainly are operational in the red and infrared part of the spectrum. The goal of the present work was to construct an all-solid-state laser system operating at deep-UV wavelengths. Solid-state UV-laser systems producing the fourth harmonic of Nd:YVO 4 are commercially available. These systems are useful for certain applications, however, their wavelength ͑266 nm͒ cannot be tuned or scanned. The development of tunable UV lasers has been reported by the group of Hänsch. 1,2 Bourzeix et al. 3 reported on a fully solidstate UV-laser system, generating the fourth harmonic of a Ti:Sapphire laser. We report on third-harmonic generation of light from a tunable continuous-wave ͑cw͒ Ti:Sapphire ͑Ti:S͒ laser. This is achieved using two steps. First, secondharmonic light is produced using a LBO crystal inside an external enhancement cavity ͑EEC͒. Subsequently, this second-harmonic light is coupled into a second EEC, together with the fundamental light. Here, the sum frequency is generated in a BBO crystal. The power P 3 generated in the sum-frequency process in the BBO crystal is given byHere, P and P 2 are the incident fundamental and secondharmonic power, respectively, and ␥ is the nonlinear coefficient of the process. Resonantly enhancing both wavelengths inside a cavity leads to a high conversion efficiency for the sum-frequency process, expressed bywhere, A and A 2 are the cavity enhancement factors for the fundamental and second-harmonic waves and, now, P and P 2 are the respective powers of the light coupled into the cavity. Sum-frequency generation with two diode lasers was realized by Sayama and Ohtsu.4 Doubly resonant sumfrequency light using two Nd:YAG lasers was generated by Kaneda and Kubota.5 Also, by combining a Ti:S and a diode laser, a narrow-band cw UV source with several tens of milliwatts output power was designed by Fujii et al. 6 Thirdharmonic generation using only a single Ti:S laser was demonstrated by Sayama and Ohtsu, 7 producing 8 nW of deep-UV radiation. In the present work, doubly resonant sum-frequency generation using a single Ti:S laser is demonstrated. The doubly resonant cavity is equipped with two Brewster plates to compensate for the dispersion in the crystal. The result is a compact narrow-band (⌫Ϸ3 MHz), tunable cw laser capable of producing 175 mW of output power in the deep UV. A schematic of the setup is shown in Fig. 1. Narrow-band 817 nm light from a tunable cw Ti:S laser ͑Coherent 899-21͒, which is pumped by a...

Diffuser heads whose angular response is proportional to the cosine of the zenith angle are needed for global irradiance measurements. Various material samples were measured for their transmission properties to find out the most promising material candidate for use in an improved solar UV diffuser. Novel bubbled quartz materials were found to be attractive alternatives to the traditional PTFE materials for this purpose. A 3D Monte Carlo particle tracing software was constructed and used to optimize the diffuser design. Integrated cosine error of 2.3 % was measured with a raised flat diffuser on a prototype detector. The preliminary simulation results indicate that integrated cosine error can be lowered to 1.7 % or below simply by adjusting the dimensions of a flat diffuser. Integrated cosine error of 0.8 % or below can be reached with shaped diffusers.