3RD EXCIMER CONTINUA IN NEON AND ARGON

The emission of the third continuum of argon in the wavelength range b etween 175 and 250 nm and the vacuum ultraviolet emission of neon (lam bda < 100 nm) has been studied by time-resolved optical spectroscopy. The target gases at pressures between 2 and 100 kPa were excited with a pulsed beam of 100 MeV S-32(9+) ions from the Munich Tandem van de G raaf accelerator. Wavelength spectra recorded in different time window s after the 2-ns beam pulses show that two different components contri bute to the third continuum of argon. A radiative lifetime of 5.71 +/- 0.08 ns for the Ar-2(2+) molecule and a rate coefficient k3 = (1.46 /- 0.12) x 10(-30) cm6/s for the reaction Ar2+ 2Ar --> Ar-2(2+) + Ar w ere obtained from the pressure dependence of time spectra at a wavelen gth of 190 nm. From time- and pressure-dependent studies of the third continuum emission of neon at a wavelength of 99 nm, rate coefficients k2 = (3.6 +/- 0.3) x 10(-13) cm3/s for the bimolecular reaction Ne2+ Ne --> 2Ne+ and k3 = (2.84 +/- 0.09) X 10(-31) cm6/s for the termole cular reaction Ne2+ + 2Ne --> Ne2(2+) + Ne were determined.