meyer_2008

M. Meyer, D. Cubaynes, D. Glijer, J. Dardis, P. Hayden, P. Hough, V. Richardson, E. T. Kennedy, J. T. Costello, P. Radcliffe, S. Düsterer, A. Azima, W. B. Li, H. Redlin, J. Feldhaus, R. Taïeb, A. Maquet, A. N. Grum-Grzhimailo, E. V. Gryzlova and S. I. Strakhova, “Polarization Control in Two-Color Above-Threshold Ionization of Atomic Helium”, Phys. Rev. Lett. 101, 193002 (2008)

Source record · Catalogue · Review register

DOI: 10.1103/PhysRevLett.101.193002

Source kind: measurement

Recorded technique: Magnetic-bottle photoelectron spectroscopy of helium (effusive jet) ionised by the FLASH free-electron laser (single bunch, 5 Hz, 10-20 fs, about 20 uJ, 25.5 nm = 48.6 eV or 13.7 nm = 90.5 eV, bandwidth 0.5-1 %, focus about 30 um) in collinear overlap with a synchronised picosecond optical dressing laser (523 nm Nd:YLF second harmonic, about 500 uJ, 12 ps; or 800 nm Ti:sapphire, up to 2 mJ, 4 ps; focus about 50 um), both linearly polarised (about 99 %), the relative angle theta set by a half-wave plate; -60 V retardation, so only the high-energy sidebands are recorded. Theory: time-dependent second-order perturbation theory (single active electron, local potential) and the soft-photon approximation (pp. 193002-1 to -3).

Materials in structured entries: None recorded.

Dataset quantities: None recorded.

Contents: 0 datasets; 0 formulas.

Curation notes

Context only, no datasets. Identity checked on the first page (PDF p. 1): Meyer et al., Phys. Rev. Lett. 101, 193002 (2008), week ending 7 November 2008, four pages 193002-1 to -4 (PDF p. n = 193002-n). Every number below was read on the PDF’s text layer and the figure images.

WHAT THE PAPER MEASURES. Two-colour above-threshold ionisation of He 1s: one XUV photon ionises (the main line, He+ 1s) and the electron exchanges n optical photons in the continuum (sidebands SBn). Only bound-continuum and continuum-continuum steps: no bound two-photon resonance and no resonant intermediate level. The quantity measured is the dependence of the sideband yield on theta, the angle between the two linear polarisations, in arbitrary units (Figs. 3 and 4 are normalised to 1 at the maximum; Fig. 2’s spectra are in arbitrary units).

The numbers (pp. 193002-2 to -4): - low dressing field, about 8 x 10^10 W/cm2 (800 nm, 13.7 nm XUV; one sideband): sigma(theta) proportional to 3 S2 + (5 S0 + S2) cos^2 theta (Eq. 1), S_i = |T_i|^2 the squared second-order radial integrals to the s (i = 0) and d (i = 2) waves; measured contrast sigma_max / sigma_min = 3.4 +- 0.5 (theory 3), whence S0:S2 = 1.25 +- 0.3, against 0.98 (second-order perturbation theory) and 1.0 (soft-photon); at theta = 0 the s:d yield ratio 5 S0 : 4 S2 ‘of 1.5’. Recomputed: contrast (5 S0 + 4 S2) / (3 S2) = 3.4 gives S0:S2 = 1.24; S0:S2 = 0.98 gives 2.97; 5 x 1.25 / 4 = 1.56; - 25.5 nm (48.6 eV) with 523 nm dressing: S0:S2 ‘about 0.9 +- 0.3’, simulation 0.85; - soft-photon approximation (Eqs. 2-3): sigma^(n) proportional to a_n + b_n cos^2 theta, b_n / a_n = 2n at low field, a contrast of 2n + 1; - high field, about 6 x 10^11 W/cm2 (800 nm, 13.7 nm; up to three sidebands, Fig. 2): SB1 contrast 1.5 +- 0.3 (soft-photon 1.47); SB2 about 3.3 (calculation about 3.5), below the limit 5; - photon energies recomputed: 1239.84 / 25.5 = 48.62 eV, / 13.7 = 90.50 eV; the 90.5 eV main line at about 66 eV kinetic energy in Fig. 2 is 90.5 - 24.59 (He’s ionisation energy). The uncertainty’s level is not stated.

NOT TAKEN (no quantity; declined, TC-1011): the S0:S2 ratios, the contrasts and the s:d yield ratio are two-colour sideband ratios. No absolute quantity is printed: no two-photon (XUV + optical) cross section, no absolute amplitude T_i or phase, no generalised cross section; the S_i appear only as ratios. The figures carry no absolute scale, so nothing would be digitised.

FOR OEP 8 AND OEP 6. Not a test of either model’s bound two-photon physics: the paper probes free-free transitions far above threshold (about 60-66 eV electrons at 90.5 eV). One remark bears on excited-level photoionisation (OEP 8’s Gamma^PI): it quotes Johansson et al. (Eur. Phys. J. D 22, 3 (2003), not in the library) for resonant two-colour ionisation through He 1snp 1P (n = 2, 3), where the d-wave cross section is ‘more than 10 times higher’ than the s-wave near threshold (p. 193002-3); a partial-wave ratio, not an absolute cross section.

Two-colour references the paper cites that the library does not hold: R. Taïeb et al., Phys. Rev. A 62, 013402 (2000) (the second-order radial integrals of Eq. 1); A. Maquet and R. Taïeb, J. Mod. Opt. 54, 1847 (2007) (the soft-photon approximation); P. O’Keeffe et al., Phys. Rev. A 69, 051401(R) (2004); O. Guyétand et al., J. Phys. B 38, L357 (2005) and 41, 051002 (2008); E. S. Toma et al., Phys. Rev. A 62, 061801 (2000); T. E. Glover et al., Phys. Rev. Lett. 76, 2468 (1996).

Recorded bibliographic identity status: VALIDATED. 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.