johansson_2003#
A. Johansson, M. K. Raarup, Z. S. Li, V. Lokhnygin, D. Descamps, C. Lyngå, E. Mevel, J. Larsson, C.-G. Wahlström, S. Aloise, M. Gisselbrecht, M. Meyer and A. L’Huillier, “Two-color pump-probe experiments in helium using high-order harmonics”, Eur. Phys. J. D 22, 3-11 (2003)
Source record · Catalogue · Review register
DOI: 10.1140/epjd/e2002-00213-1
Source kind: measurement
Recorded technique: Two-colour (1+1’) pump-probe ionisation of helium in an effusive jet (500 um orifice, 10^-6 to 1 x 10^-4 mbar chamber pressure), He+ detected by time of flight. Pump: the 13th harmonic (21.22 eV, 1s2p 1P) of a distributed-feedback dye laser near 759 nm, or the 14th (23.09 eV, 1s3p 1P) of the 753 nm dye laser mixed with its second harmonic, generated in a krypton jet (about 5 x 10^14 W/cm2), about 30 ps, about 5 x 10^6 photons per pulse in the chamber, 3.5 pm (1.3 meV) FWHM, about 500 um across. Probe: 70 ps, linearly polarised, 355, 266 or 532 nm from the picosecond Nd:YAG pump laser (or the dye fundamental), about 100 um across, at 45 degrees to the harmonic beam, delay line and half-wave plate. Lifetimes from the decay of the ion yield with delay; absolute cross sections from the saturation of the ion yield with probe energy at 230 ps delay, fitted with the three-dimensional overlap integral of Eq. (4) (pp. 4-8).
Materials in structured entries: He
Dataset quantities: excited_state_photoionization_cross_section, radiative_lifetime
Contents: 3 datasets; 0 formulas.
Curation notes#
Identity checked on the first page (PDF p. 1): Johansson et al., Eur. Phys. J. D 22, 3-11 (2003), DOI 10.1140/epjd/e2002-00213-1; received 3 June 2002, published online 22 October 2002. Nine PDF pages, journal page = PDF page + 2. This is the paper meyer_2008 (TC-1033) cites as ‘Eur. Phys. J. D 22, 3 (2003)’: volume and first page agree. Every number below was read on the PDF’s text layer and, for Table 1, on the table image.
WHAT IS MEASURED. One-photon (XUV) excitation of He 1s2p 1P1 or 1s3p 1P1 from the ground state, then one-photon ionisation of the excited level by a delayed probe: a (1+1’) resonant two-colour scheme, not a bound two-photon resonance. Levels (NIST ASD, held in src/optmat/data/external/nist_asd/He_I_levels.tsv): 1s.2p 1P*1 at 171134.894 cm^-1, 1s.3p 1P*1 at 186209.362 cm^-1; the paper’s 21.22 and 23.09 eV.
DATASETS. - tau (radiative_lifetime, ns, label, primary): p. 7, ‘lifetimes of 0.57 +- 0.03 ns for the 1s2p state and 1.76 +- 0.1 ns for the 1s3p state’, from the slope of the logarithmic decay over more than 4 lifetimes (Fig. 6), at 7 x 10^-6 mbar (1s2p) and 2 x 10^-5 mbar (1s3p); the abstract states ‘a precision of about 15%’ for both, wider than the printed +- (5-6 %). The level of the +- is not stated. Not extrapolated to zero pressure; the slopes do not change between 6 x 10^-5 and 1 x 10^-4 mbar (Fig. 7, p. 8), and radiation trapping and pressure broadening are judged insignificant (p. 9). The 1s2p value repeats Larsson et al.’s 0.57 ns (+-5 %, J. Phys. B 28, L53 (1995), the same group, not in the library), perhaps the same measurement. Check against NIST (the held He_I_lines.tsv, 40-60 nm only): 1/A(1s2p 1P1 -> 1s2 1S0) = 1/1.7989e9 s^-1 = 0.5559 ns and 1/A(1s3p 1P1 -> 1s2) = 1/5.6634e8 s^-1 = 1.7657 ns; the other branches (to 1s2s, 1s3s), not held, only shorten these, so they are upper bounds. Both measured values agree within their +-. - sigma_1s2p, sigma_1s3p (excited_state_photoionization_cross_section, Mb, against the probe wavelength, primary): Table 1 (p. 8, tbl_c7aba2f99989), ‘sigma_par (Mb)’, the absolute cross sections with the pump and probe polarisations PARALLEL (the table’s caption); ‘total uncertainty ... about 25%’ (p. 8), its level not stated. 1s2p: 16.6 Mb at 355 nm, 6.6 at 266; 1s3p: 24.4 at 752, 10.5 at 532, 4.2 at 355. The probe wavelengths are printed to 1 nm and their medium is not stated (the Nd:YAG harmonics’ nominal names, and the 752 nm dye fundamental, 14 x 53.703 = 751.8 nm); the record keeps the default (vacuum), the difference (0.1-0.2 nm) lying below the printed digits. The excess energies E_exc of the table are recomputed in the script from the vacuum wavelengths and NIST’s levels and He ionisation energy (24.587389 eV): 0.123, 1.292, 0.148, 0.830, 1.992 eV against 0.12, 1.29, 0.15, 0.83, 1.99 (each within 0.003 eV). The paper presents these as the results of the measurements of Gisselbrecht et al. [16] (Phys. Rev. Lett. 82, 4607 (1999), the same group, not in the library), described here in detail (p. 8): DOUBT, they may be that paper’s numbers, in which case the two must never be fitted side by side. The initial level is ALIGNED (M = 0 along the pump’s linear polarisation), so sigma_par is not the isotropic cross section: by Eq. (7) sigma(theta) = sigma_s + sigma_d + 2 (sigma_s + sigma_d / 10) P2(cos theta), sigma_par = 3 sigma_s + 1.2 sigma_d and sigma_perp = 0.9 sigma_d; with the theoretical d/s = 13 (p. 9) sigma_iso = sigma_s + sigma_d = 0.753 sigma_par (derived here, not taken). For OEP 8’s Gamma^PI_f of a level excited from a J = 0 ground state by linearly polarised light and ionised by the same polarisation, sigma_par is the relevant one.
CHECKED (tools/extract/johansson_2003.py, checks()): - Eq. (7) from Eqs. (5)-(6): with A20 = -sqrt(2), the 6j symbols {1 1 2; 1 1 0} = 1/3 and {1 1 2; 1 1 2} = 1/30 give sigma_iso [1 + 6 sum_L 6j(L) sigma_L / sigma_iso P2] = the printed form; d/s = 13 gives sigma_par / sigma_perp = 18.6 / 11.7 = 1.590 (printed ‘1.6’); d/s = 20 gives 1.500; - p. 7: 16.6 Mb at 355 nm (3.493 eV) and 5 x 10^8 W/cm2 is sigma I / (h nu) = 14.8 ns^-1, against the printed Gamma_r^UV(0) = 13 ns^-1 (12 % lower; DOUBT, the intensity definition is not given); 13 ns^-1 x 70 ps = 0.91 (printed 0.9); - the widths at the 1s2p line (58.433 nm, NIST): 3.5 pm = 1.27 meV (printed 1.3), 5.7 pm = 2.07 meV (2.0), 0.3 pm = 0.109 meV (0.11); - the lifetimes against NIST’s 1/A above.
DOUBTS. The dye wavelengths are rounded or approximate: the 13th harmonic of 759 nm is 21.236 eV, 18 meV above the 1s2p line (21.218 eV), and the 14th of 753 nm is 23.052 eV, 35 meV below 1s3p (23.087 eV), both far outside the 1.3 meV harmonic width; the lines need 759.6 and 751.8 nm. The abstract’s probe range ‘between 1.6 and 4.5 eV’ ends below 266 nm’s 4.66 eV. Fig. 11 (p. 9): the caption calls the solid curve ‘the theoretically predicted variation’, the text (p. 8) ‘the fit to the experimental data points, indicated by the solid curve’, yielding d/s = 20/1. Read by eye from the image, the curve runs from about 48 (0 degrees) to about 30.5 (90 degrees), a contrast of about 1.57: that of d/s = 13 (1.59), not 20 (1.50), so the curve is the theory’s. The figure does not say which level or probe wavelength it is.
NOT TAKEN: - the partial-wave ratio sigma_d / sigma_s = 20/1 measured (p. 8, ‘statistical error of about 25%’), 13/1 theoretical (Chang and Fang [17]), and sigma_par / sigma_perp = 1.6: partial-wave ratios of a two-colour process (no quantity; declined, TC-1011). meyer_2008 (TC-1033) quotes this paper’s d-wave as ‘more than 10 times higher’ than the s-wave: consistent with both 20/1 and 13/1; - the light shift of the 1s2p line under the 355 nm probe (Fig. 9, p. 9): broadened to 5.7 pm (2.0 meV) FWHM (the ‘ionization width’, calculated, 5.6 pm) and shifted 0.3 pm (0.11 meV) to the blue at an estimated 5 x 10^8 W/cm2, against Eikema et al.’s 0.015 pm for the same intensity at 292 nm. Not light_shift_coefficient: that quantity is the shift of a multiphoton transition per unit intensity of the EXCITING light, and here the shifting field is a second colour; the shift is a fifth of the harmonic’s width and twenty times Eikema et al.’s, so it is not a measurement of a polarisability either; - the ‘direct two-photon ionisation’ spike at zero delay (Figs. 7-8): ion yields in arbitrary units, explained by a rate-equation model (Eqs. 1-3) with AC-Stark broadening and XUV absorption in the gas; no cross section is printed; - Figs. 3-11: arbitrary units, or delays and spectra.
FOR OEP 8. Not a test of the two-photon coupling: no bound two-photon resonance is driven. It supplies the excited-level photoionisation of He 1s2p and 1s3p near threshold (OEP 8’s Gamma^PI_f = sigma^PI_f Phi, for levels it does not model, since OEP 8’s helium level is 1s2s) and the 1snp lifetimes, and shows the size of the AC-Stark broadening of a resonance by an ionising probe: Gamma^PI(0) about 13-15 ns^-1 at 5 x 10^8 W/cm2, a 2 meV width, the Im alpha_f part of OEP 8’s Eq. (6).
References the paper cites that the library does not hold: Gisselbrecht et al., Phys. Rev. Lett. 82, 4607 (1999) (the absolute cross sections); Larsson et al., J. Phys. B 28, L53 (1995) (1s2p lifetime); T. N. Chang and T. K. Fang, Phys. Rev. A 52, 2052 (1995) (the theory, d/s = 13); R. C. G. Ligtenberg et al., Phys. Rev. A 49, 2363 (1994) (lifetimes); K. S. E. Eikema et al., Phys. Rev. A 55, 1866 (1997) (the light shift at 292 nm); S. Baier et al., J. Phys. B 27, 3363 (1994) (Eq. 5).
Recorded bibliographic identity status: VALIDATED. This concerns identification of the source; it does not establish the scientific correctness of its contents.
Datasets#
johansson_2003/tau#
{
"id": "tau",
"material": "He",
"table": "text",
"quantity": "radiative_lifetime",
"unit": "ns",
"abscissa": "label",
"use": "primary",
"parameters": {
"method": "measured: harmonic (XUV) excitation, delayed 355 nm (1s2p) or 532 nm (1s3p) photoionisation, He+ yield against delay; low pressure, not extrapolated (slopes pressure independent, Fig. 7)"
},
"uncertainty": {
"column": true,
"level": "not stated"
}
}
2 inline points in the source record.
p. 7 (Sect. 3): 0.57 +- 0.03 ns (1s2p 1P) and 1.76 +- 0.1 ns (1s3p 1P), the slope of the logarithmic decay of the He+ yield with pump-probe delay (Fig. 6) at 7e-6 and 2e-5 mbar; level of the +- not stated (the abstract: ‘about 15%’). NIST 1/A to the ground state: 0.5559 and 1.7657 ns, upper bounds (the record’s notes).
johansson_2003/sigma_1s2p#
{
"id": "sigma_1s2p",
"material": "He",
"file": "He/johansson_2003__sigma_1s2p.csv",
"table": "tbl_c7aba2f99989",
"quantity": "excited_state_photoionization_cross_section",
"unit": "Mb",
"abscissa_unit": "nm",
"wavelength_medium": "vacuum",
"use": "primary",
"parameters": {
"initial_level": "He 1s2p 1P1 (171134.894 cm-1), aligned: M = 0 along the pump's linear polarisation",
"polarization": "linear, probe parallel to the pump (sigma_par)",
"method": "measured: saturation of the (1+1') ion yield with probe energy at 230 ps delay, fitted with the three-dimensional overlap integral (Eq. 4)"
},
"uncertainty": {
"relative": 0.25,
"level": "not stated"
}
}
Table 1 (p. 8), ‘sigma_par (Mb)’: 16.6 Mb at 355 nm (E_exc 0.12 eV) and 6.6 Mb at 266 nm (1.29 eV), pump and probe polarisations parallel. ‘Total uncertainty ... about 25%’ (p. 8). Possibly the numbers of Gisselbrecht et al. 1999 (not in the library; the record’s notes).
johansson_2003/sigma_1s3p#
{
"id": "sigma_1s3p",
"material": "He",
"file": "He/johansson_2003__sigma_1s3p.csv",
"table": "tbl_c7aba2f99989",
"quantity": "excited_state_photoionization_cross_section",
"unit": "Mb",
"abscissa_unit": "nm",
"wavelength_medium": "vacuum",
"use": "primary",
"parameters": {
"initial_level": "He 1s3p 1P1 (186209.362 cm-1), aligned: M = 0 along the pump's linear polarisation",
"polarization": "linear, probe parallel to the pump (sigma_par)",
"method": "measured: saturation of the (1+1') ion yield with probe energy at 230 ps delay, fitted with the three-dimensional overlap integral (Eq. 4)"
},
"uncertainty": {
"relative": 0.25,
"level": "not stated"
}
}
Table 1 (p. 8), ‘sigma_par (Mb)’: 24.4 Mb at 752 nm (E_exc 0.15 eV), 10.5 at 532 nm (0.83 eV), 4.2 at 355 nm (1.99 eV), pump and probe polarisations parallel. ‘Total uncertainty ... about 25%’ (p. 8). Possibly the numbers of Gisselbrecht et al. 1999 (not in the library; the record’s notes).
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.