Characteristics of electron-beam-excited Kr*2 at low pressures as a vacuum ultraviolet source

Abstract

The performance of Kr*2 as a 146 nm fluorescence or laser source when pumped by a low-current, long-pulse electron beam has been determined. The fluorescence efficiency of Kr*2 is near the theoretical limit of ∼46% at modest pressures over a range of pump rates up to 3×105 W/cm3. Lasing could not be achieved under the conditions studied here. An improved kinetics and extraction code has been developed to model the performance of the Kr*2 system. A key component of the model is a more detailed treatment of the interactions between secondary electrons and excited atomic and molecular xenon states. Estimated rates for these processes are presented. With this model, good absolute agreement of model predictions with experimental results has been obtained at pressures as low as 0.5 atm.

A kinetic model for the formation of excimers

“…In order to fit the present experimental data a rate constant for the spin flipping of 5 × 10 −8 cm 3 s −1 was assumed. This value is somewhat smaller than the corresponding rates for krypton and xenon [23,24]. The thermolecular reaction of Ar * with argon leads to vibrationally excited excimers, designated by Ar * 2 ( 3 u , h).…”

“…An efficient spin flip can only be initiated by collisions with the plasma electrons. The spin flip has been discussed by Werner et al [20] and its rate constant for krypton and xenon was deduced from the measurements by Ekstrom et al [23,24]. Whereas in slightly excited argon [18] the fluorescence decay contains two components with drastically different time constants (10 5 and 10 8 s −1 ), in highly excited argon in general only one decay component is observable, with a decay constant in the range 10 7 -10 8 s −1 .…”

Kinetics of Ar*2in high-pressure pure argon

“…Secondly, the dimer lasers can deliver more energetic quanta than those of the rare gas halide lasers, which is more favourable for applications in atomic or molecular photoionization, photodissociation, and photochemical reactions. Thirdly, a fluorescence efficiency as high as 50% can be obtained in these systems [7][8][9]. Such efficient VUV light sources could find wide applications ranging from dermatology to photo-lithography.…”

Nanosecond-pulsed dielectric barrier discharges in Kr/Cl2for production of ultraviolet radiation

“…2 ) because harpooning (reaction (R27) in table 2) is always much more important (see [29] for more details). At P Tot = 50 mbar and P Cl 2 = 0.3 mbar (0.6% of Cl 2 ), losses of Kr * by spontaneous emission and by three-body excimer formation [39] each account for only about 2% of the total Kr * loss. In this estimate, the radiation loss term was calculated using an effective decay frequency taking into account the radiation imprisonment.…”