talebpour_1996

A. Talebpour, C.-Y. Chien and S. L. Chin, “The effects of dissociative recombination in multiphoton ionization of O2”, J. Phys. B: At. Mol. Opt. Phys. 29, L677-L680 (1996)

Source record · Catalogue · Review register

DOI: 10.1088/0953-4075/29/18/002

Source kind: measurement

Recorded technique: O2+ and Xe+ ion yields against intensity over eight orders of magnitude (Fig. 1): Ti:sapphire laser, 800 nm, ‘transform-limited pulse length of 220 fs’, linearly polarised (Fig. 1 caption), f/100 focusing into an ultra-high-vacuum chamber (background ~2 x 10^-9 Torr), 60 cm time-of-flight mass spectrometer; curves joined from intensity scans at fill pressures from 10^-8 to 10^-4 Torr (p. L677). Compared with the ADK yield (Ammosov et al. 1986) ‘There is no shift in intensity’ (Fig. 1 caption).

Materials in structured entries: None recorded.

Dataset quantities: None recorded.

Contents: 0 datasets; 0 formulas.

Curation notes

Journal pp. L677-L680 = pdf pages 2-5 (pdf page 1 is the publisher’s cover sheet). Identity checked against pdf p. 2 (received 29 March 1996, in final form 17 July 1996); the cover sheet’s title renders ‘O2’ as ‘o_z’. Curated 2026-10-09 (TC-961).

NOTHING IS TAKEN. The ion yields are in Fig. 1 only (a raster image, as ion signal against intensity; not digitised). The one number measured is an appearance intensity, for which no quantity exists: ‘by increasing the intensity some ions escape the neutralization process, and they can be detected. This happens experimentally at an intensity of 1.3 x 10^13 W cm^-2’ (p. L679), the O2+ appearance intensity, defined as ‘the lowest intensity at which a detectable signal is observed under our experimental capacity and conditions’ (p. L678): a property of the apparatus as much as of O2. The O2+ appearance intensity is above that of Xe+ and of Kr+ (p. L678); the intensity calibration is not described.

THE CLAIMED MECHANISM. The suppression of O2+ relative to Xe+ (equal ionisation potentials) is attributed to dissociative recombination of the returning electron with O2+: below 10^13 W cm^-2 the rescattered electron has < 1.5 eV, where the DR cross section is ‘of the order of 10^-14 cm^2’ (Bates 1994), through O2+ + e -> O2(3Sigma_u-) -> O(3P) + O(1D) + 5.0 eV (p. L679, quoted from Bates 1994; not taken: a secondary value whose original is not in the library); ‘most of the ions (not just 50%) are neutralized’ at low intensity (Brabec et al., private communication). At 10.6 um (Walsh et al. 1994) the returning electron has > 500 eV at 2 x 10^13 W cm^-2, which is why O2+ and Xe+ appear together there (pp. L679-L680).

THE MECHANISM IS NOT SUPPORTED BY LATER WORK. guo_1998 (Phys. Rev. A 58, R4271) finds the O2+ yield ‘roughly ten times below Xe+ in the unsaturated range’ with linear and with circular polarisation alike (Figs. 2-3 there), whereas circular polarisation suppresses the recollision on which dissociative recombination here depends; so the suppression is not dissociative recombination (guo_1998’s notes). talebpour_1999, by the same group, models the suppression without recombination, by an effective charge Z_eff = 0.53 of PPT ‘to simulate the effective Coulomb potential’ that depends on ‘the random orientation of the ground state neutral molecule’, and states the fragment fraction ‘O+/O2+ ~ 10^-2’. The mechanism of this Letter is therefore recorded here as a claim only; optmat takes no rate or yield from it.

FIGURE (not digitised; raster): Fig. 1, the O2+, O+ and Xe+ yields with the ADK curve, 800 nm, 220 fs, linear; the same group’s later O2 and Xe yields (talebpour_1999, 200 fs) are also figures only.

Recorded bibliographic identity status: VALIDATED_WITH_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents.

Datasets

No datasets are recorded.

Formulas

No formulas are recorded.

Corrections

No dataset errata are recorded in this source record.

Formula corrections, where recorded, appear with their formulas above. Curation notes may also discuss corrections or unresolved interpretation. Consult the review register for the checks and decisions.