Discharge singlet oxygen generator for oxygen–iodine laser: I. Experiments with rf discharges at 13.56 and 81 MHz

Abstract

The scaling on pressure for a discharge singlet oxygen generator based on the rf discharge excitation of O2 flow is studied in the context of the problem of oxygen–iodine laser pumping. With this aim, the evolution of O2(a 1 Δg) and molecules as well as O(3P) atoms in 13.56 and 81 MHz discharges at pressures up to 15 Torr has been investigated in detail. It is shown that fast quenching of O2(a1Δg) by atomic oxygen with increasing pressure and energy input causes rapid saturation of the O2(a1Δg) density in the discharge and limits the O2(a 1 Δg) yield on a rather low level of a few per cent. Covering of the discharge tube walls with mercury oxide for fast catalytic removal of oxygen atoms allows us to greatly increase the O2(a 1 Δg) yield as well as to avoid fast quenching of O2(a 1 Δg) in the early afterglow. It enables us to succeed in obtaining the rather high O2(a 1 Δg) yields at such high pressure as 10–15 Torr. So the singlet oxygen yield is ∼10–12% at ∼10 Torr. The transition to the higher frequency of 81 MHz even increases greatly the O2(a 1 Δg) yield up to ∼16%.