J. Wieser

Lyman-alpha emission via resonant energy transfer

Very intense hydrogen Lyman- light emission is observed from neon gas near atmospheric pressure containing small admixtures (per mil) of hydrogen when this gas mixture is excited by ionizing particle beams. A DC beam of 15 keV electrons or a pulsed beam of 100 MeV ions were used in different experiments for excitation. A collisional energy transfer rate constant from neon to of has been measured using time-resolved optical spectroscopy on the Lyman- line. Conversion efficiencies of particle beam power into Lyman- light of the order of 10% have been observed. No other significant radiation was emitted in the entire VUV, UV and visible spectral region. In particular, no other hydrogen lines are observed under these conditions. The selective excitation of the H(2p) level is interpreted as arising from a resonant energy transfer between excimers and hydrogen molecules.

Emission of vacuum ultraviolet radiation from neon excimers excited by a heavy ion beam

The vacuum ultraviolet emission of neon excited with a pulsed 100 MeV 32S9+ ion beam from the Munich Tandem van de Graaff accelerator was studied at pressures between 1.8 and 96.1 kPa. In the wavelength range between 70 and 110 nm the first, second, and third excimer continua were observed. From time‐ and pressure‐dependent studies of the third continuum emission at a wavelength of 99 nm, rate coefficients k2=(3.6±0.3)×10−13 cm3/s for the bimolecular reaction Ne2++Ne→2Ne+ and k3=(2.84±0.09)×10−31 cm6/s for the termolecular reaction Ne2++2Ne→(Ne2+Ne)2++Ne were determined.

Ultraviolet emission from argon water-vapor mixtures excited with low-energy electron beams

A 310-nm-ultraviolet light source operating at the OH (AΣ+2→XΠ2) transition is presented. The OH band is emitted from argon water-vapor mixtures excited with low-energy (15 keV) electron beams. The light output is studied in the argon pressure range from 250 to 1000 hPa. In this study, the highest OH band intensity was observed at the lowest Ar pressure and a water-vapor concentration of about 0.02%. An efficiency of 3% for converting electron beam power into light emission was measured under these conditions.

Heavy ion beam pumped visible laser

Heavy ion beam pumped laser action was observed in the visible spectral range. This result is encouraging for the potential development of shorter wavelength lasers pumped by heavy ion beams. The laser operated on the 585.25‐nm neon line in He‐Ne‐Ar, He‐Ne‐Kr, and He‐Ne‐Xe mixtures. The laser gas pressure was, typically, 800 hPa and the mixing ratio 92% He, 6% Ne, and 2% Ar (Kr,Xe). Quasicontinuous laser action was obtained using a chopped beam of 120‐MeV 35 Cl ions for pumping. Preliminary spectroscopic studies of the laser medium show selective excitation of the 585.25‐nm line.

Third excimer continua in neon and argon

The emission of the third continuum of argon in the wavelength range between 175 and 250 nm and the vacuum ultraviolet emission of neon (λ 32 S 9+ ions from the Munich Tandem van de Graaf 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 Ar 2 2+ molecule and a rate coefficient k 3 = (1.46 ± 0.12) x 10 -30 cm 6 /s for the reaction Ar 2+ + 2Ar → Ar 2 2+ + Ar were obtained from the pressure dependence of time spectra at a wavelength of 190 nm. From time- and pressure-dependent studies of the third continuum emission of neon at a wavelength of 99 nm, rate coefficients k 2 = (3.6 ± 0.3) x 10 -13 cm 3 /s for the bimolecular reaction Ne 2+ + Ne→ 2Ne + and k 3 = (2.84 ± 0.09) X 10 -31 cm 6 /s for the termolecular reaction Ne 2+ + 2Ne → Ne 2 2+ + Ne were determined.

Optical gain on the 476.5 nm Argon-ion laser line in a gas-target excited by a heavy ion beam

Optical gain on the 476.5 nm Ar II 4p−4s ion laser transition has been observed in argon-gas excited by 2.5 ns pulses of 90 MeV32S ions with a repetition rate of 4883 Hz. The energy per pulse was 23 μJ. The projectiles were stopped in the target at pressures between 5 and 20 kPa. Gain was determined from a measured transient increase of the intensity of a 476.5 nm probe laser beam sent along the ion beam axis and back reflected by an aluminum foil. The maximum gain observed was (0.4±0.1)×10−3 at a target-gas pressure of 5 kPa. Control experiments using krypton as target-gas were performed and yielded a null result. The optical gain observed in argon is consistent with the result from an analysis of spectroscopic studies of rare-gas targets excited by heavy ion beams.

Measurement of lifetimes and collisional rate constants for 3p levels in neon I, II and IV

Lifetimes and collisional quenching rate constants have been measured for 3p levels in Ne I, Ne II, and Ne IV. The levels were populated by direct excitation from the neon ground state using a pulsed beam of 100 MeV32S ions from the Munich Tandem van de Graaff accelerator. Beam pulses were 2 ns long (FWHM) and had a repetition rate of 78 kHz. Lifetimes were measured by time resolved optical spectroscopy. Collisional rate constants were determined from time spectra for various target gas pressures.

Emission of light from matter excited by heavy-ion beams☆

Abstract The emission of light from rare-gas targets excited by a pulsed 100 MeV 32 S 8+ beam is studied by time-resolved optical spectroscopy. A waveleng

Influence of water vapour impurities on the atomic Xe laser

The influence of water vapour impurities on the output power of the 1.73 µm 5d[3/2]1 -6p[5/2]2 Xe I laser has been studied. The laser gas was a mixture of 99.5% Ar and 0.5% Xe with a total pressure of 500 mbar and was pumped by 50 µs long 100 MeV 32 S9+ heavy ion beam pulses. The gas remained essentially at room temperature during the pumping pulses. A significant reduction of laser power was observed when water vapour at a concentration of more than 1014 cm-3 was added. A simple model assuming electron attachment and collisional quenching by water vapour as the dominant causes for reduced laser intensity was used to fit the experimental data. We obtained a rate constant for quenching the upper laser level (K H2 O Q ) of 4 × 10-9 cm3 s-1 , and a ratio of the rate constant of electron attachment to water vapour to total recombination rate of 6 × 10-16 cm3 .

Heavy ion beam excitation of rare gases

The emission of light from rare gas targets at pressures of more than 100 Pa excited by a pulsed heavy ion beam has been studied. The absolute intensity of several spectral lines has been measured as a function of time at different target gas pressures. Population densities, excitation cross sections, and rate constants for collisional quenching were determined from the line intensities and the lifetimes of the excited states.