Associative ionization in collisions of with and

Abstract

Absolute cross sections of the associative ionization in the collision of He + with H − or D − have been measured in a merged beam experiment over a relative velocity interval ranging from 0.4 to 5 × 10 6 cm s −1 . At a given relative velocity, the two cross sections significantly differ at low velocities where the cross section for HeD + formation exceeds that of HeH + by as much as 35%. The difference, however, decreases with the velocity and falls in the experimental error above 2 × 10 6 cm s −1 . In both cases the energy dependence becomes compatible at low energy with an E −1 law.

Animated-beam measurement of the photodetachment cross section ofH−

“…The standard deviation of the mean [27] is 0.02 x 10-21 m2, about 0.5% of the mean, highlighting the excellent repeatability of our measurements and providing the statistical error. Uncertainties arising from systematic effects are estimated as follows: the powermeter accuracy of 3% is given by the manufacturer; the vertical displacement of the laser beam is known with 2% precision, as estimated from the comparison of measured and calculated values; the 1% error on the current measurement is obtained by comparing the current measured by the two Faraday cups FC1 and FC2 and corresponds to the calibration accuracy of the electrometer; an uncertainty of 1% on the ions' velocity is given by the small variations of the source's acceleration voltage (4 kV); the uncertainty of 2% on the detection efficiency of the CEM has been previously established by Naji et al [25]. Each of these values provide an upper limit a+ and a lower limit to the exact value a.…”

“…The neutral hydrogen atoms fly straight through the quadrupole and are detected about 30 cm downstream by a CEM (KBL 25 RS, Dr. Sjuts Optotechnik). Two parameters affect the detection of neutrals by the CEM: the detection efficiency r) and the value of the counting rate N. The efficiency is estimated to be 0.98 ± 0.02 according to Naji et al [25], who measured the efficiency of the exact same detector model. Furthermore, test measurements for a 6-keV beam showed no significant increase of the detection efficiency, suggesting that 7 ] has reached the asymptotic regime of efficiency versus particle energy, as expected from the CEM specifications.…”

Investigation of critical parameters controlling the efficiency of associative ionization

“…With the help of the merged ion beam apparatus implanted in Louvain-La-Neuve, Belgium, we were able to investigate various combinations of reactants to form diatomics and triatomics [16][17][18][19][20][21][22][23]. Since technical details, not relevant here, were described elsewhere, for instance in [17], they will not be repeated. Among them, we select three emblematic cases to illustrate the specificities of the process.…”

Associative ionization in collisions of , with and

“…In a recent paper [1], we presented an experimental study of associative ionization in the collision of He + with H − and D − . In this paper, a new set of measurements is reported dealing with the associative ionization of H + 2 and D + 2 with H − and D − .…”

“…One of them is associative ionization in the collision of H + 2 with H − and is dealt with in this paper. The cross sections of the following reactions have been measured: The experimental set-up used for the measurements was the same as that described in [1]. A beam of H + 2 (or D + 2 ) produced by an ECR source, was merged with a beam of H − (or D − ) and the reaction products formed in a region delimited by a bias voltage were separated by a magnetic analyser and detected by a channel electron multiplier.…”