singhal_1998

R. P. Singhal, H. S. Kilic, K. W. D. Ledingham, T. McCanny, W. X. Peng, D. J. Smith, C. Kosmidis, A. J. Langley and P. F. Taday, “Comment on ‘On the ionisation and dissociation of NO2 by short intense laser pulses’”, Chem. Phys. Lett. 292, 643 (1998)

Source record · Catalogue · Review register

DOI: 10.1016/S0009-2614(98)00718-0

Source kind: measurement

Recorded technique: Laser time-of-flight mass spectrometry of NO2 (femtosecond laser mass spectrometry, FLMS) at 248, 375, 496 and 750 nm, pulse durations from 90 fs to several picoseconds, intensities up to 2.5 x 10^14 W/cm2 (p. 644); the details are in the authors’ earlier papers (their Refs. 2-6), not here.

Materials in structured entries: None recorded.

Dataset quantities: None recorded.

Contents: 0 datasets; 0 formulas.

Curation notes

A comment on K. Vijayalakshmi, C. P. Safvan, G. Ravindra Kumar and D. Mathur, Chem. Phys. Lett. 270, 37 (1997) (35 ps at 532 and 1064 nm, 10 ps at 590 nm, up to 10^14 W/cm2), which is not in the library. CPL 292 pp. 643-646 = pdf pages 1-4.

IDENTITY (TC-968): the library holds this paper under an unverified key with no metadata. Checked on pdf page 1: the title (printed with ‘NO’ and a subscript 2), the nine authors, ‘Chemical Physics Letters 292 (1998) 643-646’, 14 August 1998, received 3 April 1997, final form 19 October 1997, and ‘PII: S0009-2614(98)00718-0’, which is the DOI’s suffix. VALIDATED_WITH_WARNINGS: identity established from the page by the curator, the library’s own record still unverified.

WHY NOTHING IS TAKEN. The new measurements are in figures only, both raster images: Fig. 1, the ratio of NO2+ to NO+ yields against intensity at 750 and 375 nm, 90 fs (‘There is no dependence of the ratio on laser intensity for 750 nm. For 375 nm, the ratio shows a modest increase with intensity and reflects the onset of NO saturation’); Fig. 2, the same ratio against pulse duration (90 fs to 1.5 ps) at 750 nm, rising ‘systematic[ally] and large[ly]’ as the pulse shortens. Fig. 3 shows CO2 spectra (90 fs against 35 ps). The numbers in the text are not fragmentation ratios: - ‘For 90 fs pulse width the ratio NO2+/NO+ shows little or no dependence on laser intensity ... However, the parent-ion yield is about 10 times larger at 750 nm than it is at 375 nm’ (p. 644); whether the factor 10 is of the ratio or of the NO2+ yield is not said (Fig. 1 plots the ratio). - For 90 fs, ‘the intensity dependence of both NO and NO2 ion production [is] 3.0-3.5 for 750 nm and 2.2-2.9 for 375 nm’ (p. 644; log-log slopes; no quantity holds them). - The intensity range: ‘up to 2.3 x 10^14 W cm^-2’ (abstract) and ‘up to 2.5 x 10^14’ (p. 644), as printed.

QUOTED, NOT TAKEN: Vijayalakshmi et al.’s slopes of NO2+/NO+, n = 2.4 (532 nm) and 5.5 (590 nm), and from them n = 8.4 for NO2+ with He & Becker’s NO slope 2.9 (pp. 643-644); Keldysh parameters of their data 4.30, 3.88 and 2.15 at 532, 590 and 1064 nm (p. 645, computed with the printed formula gamma = [E_i / (1.87e-13 I lambda^2)]^(1/2), E_i in eV, I in W/cm2, lambda in um). The paper argues that in the multiphoton regime NO2 is ionised before it dissociates in a 90 fs pulse, so short pulses keep the parent ion, and that the intensity dependence of the ratio in Vijayalakshmi et al.’s picosecond data cannot come from ionisation followed by dissociation.

FIGURES FOR LATER (TC-968; raster): Fig. 1 (NO2+/NO+ against intensity, 750 and 375 nm, 90 fs) and Fig. 2 (against pulse duration, 750 nm). The intensity is not calibrated in this comment.

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.