The optogalvanic spectra of uranium and thorium are convenient sources of lines with which to calibrate wavemeters for high-resolution laser spectroscopy. We used hollow-cathode lamps for both uranium and thorium to observe the spectra, using a single-frequency cw dye laser operating over the wavelength range 694-755 nm. Eight uranium and seven thorium lines were measured with an accuracy of a few parts in 10 8 with our Fabry-Perot wavemeter. The estimated uncertainty of the measurements is 0.0002 cm Ϫ1 for both species. The results were compared with several previous measurements of these lines and were found to be in good agreement with values determined by Fourier-transform spectroscopy.

We have observed broadening and shift of the 2S-4S Doppler-free two-photon transition of atomic Li by collisions with neon and argon buffer gases in a heatpipe oven. Measured broadening and shift rates are presented and compared with theoretical predictions calculated in the impact approximation using three different interaction potentials. A superposition of polarization and modified Fermi potentials gives good agreement with the experimental data.

We have developed a slow, highly collimated, and bright sodium atom beam suitable for orientation and alignment studies in cold collisions. A combination of transverse-optical collimation, longitudinal cooling, rapid decoupling from the longitudinal cooling cycle, and a final ''optical-force extrusion'' stage produces an atom density of 1ϫ10 10 cm Ϫ3 within a beam-divergence solid angle of 2ϫ10 Ϫ6 sr. Rapid Zeeman-cooler decoupling results in a narrow laboratory velocity distribution of 5 m/s full width at half maximum and a cold binary intrabeam collision temperature of 4 mK.

We report measurements of cold photoassociative ionization ͑PAI͒ spectra obtained from collisions within a slow, bright Na atomic beam. A high-brightness atom flux, obtained by optical cooling and focusing of the atom beam, permits a high degree of alignment and orientation of binary collisions with respect to the laboratory atom-beam axis. The results reveal features of PAI spectra not accessible in conventional magnetooptical trap studies. We take advantage of this high degree of alignment to selectively excite autoionizing doubly excited states of specific symmetry.

The spectra of uranium and thorium are convenient sources of reference lines for wavelength calibration at the level of a few parts in 10 8. We observed these spectra by laser optogalvanic spectroscopy in commercial hollow-cathode lamps using a single-frequency cw dye laser operating over the wavelength range 422 nm to 462 nm. Ten uranium and eight thorium lines were measured with an estimated uncertainty of 0.0003 cm −1 by using our Fabry-Pérot wavemeter. The results are compared to previous measurements of these lines and are found to be in good agreement with, and an order of magnitude more accurate than, values determined by Fourier-transform spectroscopy.