walker_1994

B. Walker, B. Sheehy, L. F. DiMauro, P. Agostini, K. J. Schafer and K. C. Kulander, “Precision measurement of strong field double ionization of helium”, Phys. Rev. Lett. 73, 1227 (1994)

Source record · Catalogue · Review register

DOI: 10.1103/PhysRevLett.73.1227

Source kind: measurement

Recorded technique: He+ and He2+ yields against peak intensity over twelve orders of magnitude of counting range, and photoelectron spectra: 780 nm, 160 +- 30 fs pulses, 1 kHz, up to 1.3 mJ (pulse-to-pulse fluctuation < 1.7 % over 10^6 shots), linear polarisation (extinction ratio > 100), 10 cm focal-length doublet into an ultrahigh vacuum (10^-10 torr); 99.999 % helium scrubbed to < 0.1 ppm of O2, H2, H2O, CO2 and hydrocarbons; 30 cm time-of-flight mass spectrometer (m/dm > 300, H2+ and He2+ separated), 1 ns binning of discriminated events at <= 0.25 events per shot; >= 60 000 shots per point, five scans with three spot sizes (p. 2). Compared with single-active-electron (SAE) TDSE yields (Schafer et al. 1993) and ADK (pp. 2-3).

Materials in structured entries: None recorded.

Dataset quantities: None recorded.

Contents: 0 datasets; 0 formulas.

Curation notes

Journal pp. 1227-1230 = pdf pages 1-4. Identity checked against pdf p. 1 (the library flags a year hint of 2011, the download date; the page prints 29 August 1994).

WHY NO YIELDS ARE TAKEN. The yields are in Fig. 1 only (He+ and He2+ ion signal against intensity, 10^14 to 10^16 W/cm^2, with the SAE (solid) and ADK (dashed) He+ curves, the NS He2+ model curve (dotted) and the calculated sequential He2+ yield), and the He2+(NS)/He+ ratio in Fig. 3 (with 1 standard deviation error bars); not digitised. The ion signal is not absolute.

PULSE. ‘160 +- 30 fsec, 780 nm’ (text p. 2, and the abstract’s ‘160 fs’), but the Fig. 1 caption says ‘100 fsec’: an inconsistency of the paper; the text’s 160 fs is the stated measurement.

CALIBRATION (p. 2). ‘The laser intensity is calibrated by measuring the short pulse resonant photoelectron spectrum of xenon as a function of pulse energy and concurrently recording the xenon and helium ion yields. The calibration is corroborated by a spot size measurement and accurate to approximately 30%.’ In Figs. 1 and 3 ‘The measured intensities are multiplied by 1.15’ (captions), i.e. the plotted intensity scale is the measured one times 1.15 (the paper does not say why; the factor lies within the stated 30 %). e/m detection sensitivity 1:1.25 (He+:He2+), ‘based on saturated yields’.

TEXT VALUES (p. 2-4; not taken as data, since no quantity holds a saturation intensity or a yield ratio): ‘The He+ yield increases nonperturbatively up to a measured saturation intensity of 8 x 10^14 W/cm^2. Beyond this point the yield increases as I^(3/2)’. He2+: NS production at (1.5-8) x 10^14 W/cm^2, saturated regime (0.8-3) x 10^15 W/cm^2, sequential production above 3 PW/cm^2 and saturation at 8 PW/cm^2. ‘the ratio exhibits a gentle slope of only I^1.3. The ratio is constant (0.0020 [3]) from about 5 PW/cm^2 until the sequential production of He2+ becomes significant’ (p. 3, as printed; Fig. 3 shows the plateau from about 0.5 PW/cm^2 and sequential production is said to start at 3 PW/cm^2, so ‘5 PW’ reads as a slip for 0.5 PW); the conclusion: ‘a saturated value of 0.0020’ (p. 4). The ion curves vary by 7 orders of magnitude between 0.15 and 5.0 PW/cm^2 (p. 3). SAE agrees with the He+ yield over the whole range, ADK falls below it at low intensity, ‘the multiphoton contribution becoming increasingly important below 0.5 PW/cm^2’ (p. 2); the tunnelling fraction of the SAE rate rises from 0.05 to 1 over the range (p. 3). The rescattering threshold 3.2 U_p >= 54.4 eV would be 0.3 PW/cm^2 (0.23 allowing excitation to 41 eV and barrier suppression); the data go down to 0.14 PW/cm^2 without a threshold (p. 3); U_p = 5.7 eV at 10^14 W/cm^2 and 780 nm (ref. 10). This paper’s He+ saturation is the reference against which larochelle_1998 calibrates its intensities (ADK’s He saturation).

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.