No abstract

The spectra emitted in the decay of the first excited states of the (RgA)+ ions with Rg = Ar, Kr or Xe and A = Li, Na, K, Rb or Cs have been investigated. The emission of these excimer-like ions is in the vacuum ultraviolet region and hence they are of interest for possible lasers operating in the vuv. Each ion decays by emission of 3 or 4 continua.Based on recent ab initio calculations by Markert er a1 the transitions are assigned to the decay of the 0 = 1 and O+ levels of the (RgA)+ ions correlating with the asymptotic states Rg+(2P3,2)+A. In the (ArA)+ ions the doublet expected for the (RgA)+ ions with a Rg+(*P,,*) + A asymptotic state was also observed.

The profile, density, and temperature of a supersonic rare-gas jet was determined applying methods of nuclear physics and optical spectroscopy. The jet was produced in the windowless gas target facility RHINOCEROS and the heavy-ion particle beams were provided by the Stuttgart DYNAMITRON accelerator. Maximum densities in the range of 1017 to some 1018 particles/cm3 could be achieved in a gas jet of about 2.6 mm diam (FWHM). In a supersonic helium jet a cooling of the gas down to 45 K was observed. These results were compared with theoretical calculations.

Rare gases have been excited by dc ion beams of He+, Ne+ and Ar+ in the energy range 0.5–3.9 MeV using the Stuttgart DYNAMITRON accelerator and the gas target system RHINOCEROS. The VUV emission of the first, second and third continua was observed in the wavelength range between 50 and 300 nm. Especially the third continuum of neon could be observed at 99 nm for the first time in this way. The relative intensities of the continua depend strongly on the mass of the exciting ion and on the presence of contaminations. The observations support strongly the assignment of the third continuum to the radiative decay of Rg2+2 ionic excimers.

Ionic rare gas alkali excimers Rg+A were produced by exciting Rg/A mixtures in a buffer gas atmosphere by means of an ion or electron beam. As a representative candidate the formation of Kr+K decaying at 135 nm was investigated. The rate constant k(He) for the main reaction Kr++K→Kr+K was determined varying the buffer gas density [He] between 1017 and 1020 cm−3. Values between k(He)=1×10−11 and 5×10−10 cm3 s−1 were observed. At high buffer gas densities the quantum yield ηq for the emission of the 135 nm radiation depends on the ratio [K]/[Kr]. At the optimum value, [K]/[Kr]=0.06, an absolute yield of ηq=1.5% was obtained. Up to a deposited energy of 3 mJ/cm3 the quantum yield is independent on the excitation density. For neon as buffer gas the rate constants k(Ne) are smaller by about a factor of 3, while the efficiency is only slightly less than for He. Kr+K is split into five fine structure states. The quenching of these states by krypton and buffer gas causes the low quantum yield.