High resolution spectroscopy of xenon using coherent narrowband XUV radiation generated by four-wave mixing

Abstract

Absorption transitions were scanned by pulsed, narrowband, tunable coherent XUV radiation generated by two-photon resonant four-wave mixing in krypton. The four-wave mixing was accomplished by focusing two collinear beams into a chamber containing 1–5 Torr of krypton with a few Torr of argon added to Improve phase matching. One input beam was fixed at 2166.67 Å, corresponding to the 4p6 1S0 →4p5 5p[2 1/2]2 two- photon resonance in krypton. The other beam was the visible or near-IR output of a pressure- tuned dye laser. The XUV wavelength was calculated from measurements of the input wavelengths using a Fizeau-type wavemeter. Because very little xenon was required for absorption, both the generation and absorption of the XUV could be done in the same chamber, eliminating the need for differetial pumping. Thus, static pressure measurements allowed accurate determination of the xenon number density. Two well-defined absorption paths were established by a coated capillary array beam splitter for the XUV. The two signals were ratioed to obtain intensity profiles which were independent of the input intensities, and accurate cross sections were then calculated.