Geometry-independent, phase-matched measurement of a vacuum-ultraviolet oscillator strength in xenon

A new method for accurately measuring the oscillator strengths of gases is presented. The technique is based on determining the phase-matching conditions for four-wave mixing in a gas mixture. When high gas pressures are used, the measurement is independent of the detailed spatial-mode properties of the laser. By using the known refractive index of argon as a reference, the oscillator strength of the xenon ground-state-to-7s [3/2](1) transition at 117.04 nm was found to be 0.098 +/- 0.012.