Energy transfer in mercury vapour following laser excitation of the 7¹S₀state by two-photon absorption

Abstract

After excitation of the 71S0 mercury state by two photon absorption of a laser radiation at 313 nm the time integrated intensities of the 407.8 (I0) and 404.7 nm (I1) lines emitted from the 71S0 and 73S1 states were determined as functions of the pump laser intensity, I, and mercury pressure. At high pump laser intensities I0 and I1 do not follow anymore a quadratic law in I, I0 weakens to In<2 while, in contrast, I1 increases to In>2. The time evolutions of the populations of these 71S0, 73S1 states and of the 61P1, 63P0,1,2 states were determined. The set of experimental results is well reproduced by introducing collisions of two Hg(6P) atoms as well as two Hg(71S0) collisions. Effects of these collisions are discussed.

Investigation of a laser-induced ablation plume of mercury as a nonlinear medium for Vacuum UltraViolet generation

“…4). Such a slow 7s 3 S 1 population decay can be explained by cascading from higher excited levels and collisions, which populates the 7s 3 S 1 state at longer times [2]. Experimentally, we noticed that the best VUV enhancement was obtained when the ArF pulse hit the Hg surface ≈1 s before the UV and visible pulses ( fig.…”

“…For example, interference lithography of sub-100 nm patterns would require short wavelength lasers with a long coherence length, which is not the case of standard excimer lasers (ArF, F 2 ). An alternative solution consists in using visible coherent lasers followed by nonlinear conversion in gases down to the VUV.…”

Enhanced generation of vacuum-ultraviolet radiation by four-wave mixing in mercury using pulsed laser vaporization

“…Saturation behavior in two-photon resonant mixing processes is typical of the interaction of intense fields with dense gaseous media, and has been discussed by many authors [29,30]. Two-photon absorption plays a key role here since the twophoton absorption cross section for the 6 1 S 0 →7 1 S 0 transition is especially high (2.6 10 -6 s -1 .W -2 .cm 4 [31]). With UV intensities in the GW/cm 2 range (here, 3.5 GW/cm² for ω UV ), the transition can be theoretically saturated.…”

High intensity vacuum ultraviolet and extreme ultraviolet production by noncollinear mixing in laser vaporized media

“…When the 312.85 nm laser was well overlapped both spatially and temporally with the Hg plume, bright blue fluorescence was visible at the 312.85 nm focus. This fluorescence was most likely due to the fluorescence from 7 1 S 0 → 6 3 P 1 at 407.8 nm 39 and was not visible if the 312.85 nm laser wavelength was detuned or the timing between the dye lasers and the ablation laser was not optimal. The presence of the blue fluorescence was a useful visible check for correct alignment, wavelength, and timing.…”