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 `__ · :doc:`Catalogue ` · :doc:`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 :doc:`review register ` for the checks and decisions.