Optical excitation of metastable krypton using a long-lifetime vacuum ultraviolet lamp

Optical excitation of metastable krypton is a common technique in radiometric dating. The requirement of 123.6 nm vacuum ultraviolet (VUV) radiation is typically generated by gas discharge lamps. However, these lamps experience a rapid decline in light intensity over time due to the accumulation of discharge byproducts. In this study, we mitigated the accumulation of contaminants by introducing a buffer zone behind the discharge area and implementing a continuous gas refreshment system. As a result, the VUV lamp maintained 30 % of its initial intensity after operating for 550 h. Subsequently, the lamp was employed to optically generate metastable krypton within a cell via resonant two-photon excitation. By monitoring the laser-induced fluorescence signal, we examined the relationship between metastable krypton density and the power of an 819.2 nm laser, as well as the pressure within the cell. We uncovered the pressure dependence of VUV light utilization, identifying an optimal pressure of 80 Pa where 78 % of the VUV light was absorbed. The findings of this paper offer significant insights into enhancing the optical generation of metastable krypton flux and are applicable to the excitation of other noble gas atoms.