3RD EXCIMER CONTINUUM OF ARGON EXCITED BY A HEAVY-ION BEAM

The emission of the third excimer continuum of argon in the wavelength range between 175 and 250 nm has been studied by time-resolved optical spectroscopy. Argon gas at pressures between 5 and 100 kPa was excited with a pulsed beam of 100-MeV S-32(9+) ions from the Munich tandem van de Graaff accelerator. Wavelength spectra recorded in different time windows after the 2-ns beam pulses show that two different components contribute to the third continuum of argon. A radiative lifetime of 5.71 +/- 0.08 ns for the Ar2(2+) molecule and a rate coefficient k3 = (1.46 +/- 0.12) x 10(-30) cm-6/s for the reaction Ar2+ + 2Ar-->Ar2(2+) + Ar were determined from the pressure dependence of time spectra at a wavelength of 190 nm. Additional time spectra were measured at 210 and 230 nm.