baig_2008#
M. A. Baig, S. Mahmood, R. Mumtaz, M. Rafiq, M. A. Kalyar, S. Hussain and R. Ali, “Oscillator strength measurements of the 3p5(2P1/2) nd’[3/2]2 and [5/2]2,3 autoionizing resonances in argon”, Phys. Rev. A 78, 032524 (2008)
Source record · Catalogue · Review register
DOI: 10.1103/PhysRevA.78.032524
Source kind: measurement
Recorded technique: Two-step laser excitation with optogalvanic (ion current) detection in an argon dc discharge cell (~1 mbar, ~270 V, negative glow). The 4s[3/2]2 metastable, collisionally populated, is excited by a first dye laser (LDS 698, 532 nm pumped) to 4p’[3/2]1, 4p’[3/2]2 or 4p’[1/2]1; a second dye laser (Coumarin 480, 355 nm pumped, delayed ~3 ns, linearly polarised like the first) scans the 3p5 nd’ and ns’ autoionising series (460-515 nm) or ionises at the 3p5 2P1/2 threshold. The photoionisation cross section of each 4p’ level at the threshold is from the saturation of the ion signal with the ionising pulse energy, Z = N0 [1 - exp(-sigma U / (2 hbar omega A))] (Eq. 2, Burkhardt et al.), A = 0.002(1) cm2 from the Gaussian-beam relation (Eq. 3); the nd’ oscillator strengths are calibrated against these cross sections (Eq. 4, Mende and Kock) and corrected for the Fano profile (Eq. 5, |q| = 20-30).
Materials in structured entries: Ar
Dataset quantities: excited_state_photoionization_cross_section
Contents: 3 datasets; 0 formulas.
Curation notes#
Phys. Rev. A 78(3), 032524 (2008) = PDF pages 1-9 (article page 032524-n = PDF page n). Identity checked on the first page (PDF p. 1: journal, volume, article number, title, authors, Quaid-i-Azam University, Islamabad; received 16 June 2008, published 30 September 2008; DOI) on 2026-10-12. The cross sections were read on the rendered pages 1, 5 and 8.
LEVELS (the paper’s jK labels, a prime for the 2P1/2 core; NIST Ar_I_levels.tsv). 4p’[3/2]1 = 3s2.3p5.(2P*<1/2>).4p 2[3/2] J = 1 (107131.7086 cm-1; Paschen 2p4); 4p’[3/2]2 = 3s2.3p5.(2P*<1/2>).4p 2[3/2] J = 2 (107289.7001; 2p3); 4p’[1/2]1 = 3s2.3p5.(2P*<1/2>).4p 2[1/2] J = 1 (107496.4166; 2p2). The paper’s level energies (p. 4: 107131.707, 107289.700, 107496.416 cm-1, ‘taken from the NIST data base’) are NIST’s. None of these J = 1, 2 primed levels is one of OEP 8’s two-photon levels (4p’[1/2]0, 4p[1/2]0, 4p[3/2]2, 4p[5/2]2); they are reached in one photon from 4s[3/2]2.
THRESHOLD WAVELENGTHS. The ionising wavelengths are printed as 467.1 nm (4p’[3/2]1), 470.5 nm (4p’[3/2]2) and 475.17 nm (4p’[1/2]1) (p. 5), ‘corresponding to the 3p5 (2P1/2) ionization limit’. With the paper’s limit 128541.38 cm-1 (p. 4) they are the vacuum wavelengths of the threshold: 467.079, 470.551 and 475.173 nm (in air 466.950, 470.422, 475.042), so wavelength_medium = vacuum (467.1 and 475.17 decide it; 470.5 lies 0.05 nm below the vacuum value and 0.08 nm above the air value). NIST’s limit (Ar I ionisation energy 127109.842 + Ar II 2P1/2 1431.583 = 128541.425 cm-1) gives 467.078, 470.550 and 475.172 nm, i.e. photon energies 2.6545, 2.6349 and 2.6092 eV.
TAKEN (inline, p. 5, also the abstract p. 1): sigma = 34 +- 5 Mb (4p’[3/2]1, 467.1 nm), 31 +- 5 Mb (4p’[3/2]2, 470.5 nm), 28 +- 4 Mb (4p’[1/2]1, 475.17 nm), one dataset per level, use primary (the paper’s measurement). The +- has no stated level; the text gives the total ‘about +-18%’ from the laser energy (5 %), the beam diameter (10 %) and the detection calibration (10 %) (p. 5).
DOUBTS. (1) The conclusion (p. 8) lists the levels as ‘4p’[1/2]1, [3/2]1, and [3/2]2 as 34 +- 5, 31 +- 5, and 28 +- 4 Mb, respectively’, a different assignment from Sec. III B (p. 5) and the abstract, which agree and are followed here; Sec. III C (p. 7) also calibrates the 4p’[3/2]1 series with 34 Mb, 4p’[3/2]2 with 31 and 4p’[1/2]1 with 28. (2) The beam area is printed ‘0.002(1) cm2’ (p. 5), a 50 % uncertainty, while the error budget allows 10 % for the beam diameter (20 % in area); the stated +- may be small. (3) The measurement is in a discharge: high nd’ Rydberg members within the field-lowered threshold and the laser bandwidth are ionised too, and the paper does not say where the laser sits relative to the unresolved nd’ series (Table I resolves n <= 52, 41 cm-1 below the limit). Not corrected here. (4) p. 4 says the 715.01 nm first laser excites ‘from the 3p5 4p’[3/2]2 metastable state’; the metastable is 4s[3/2]2 (NIST: 4s[3/2]2 - 4p’[3/2]1, 1s5 - 2p4, is 714.704 nm in air, 714.901 nm in vacuum; the printed 715.01 nm matches neither).
FINDING: AGAINST petrov_2011 (TC-1067), THE CALCULATION OEP 8 USES FOR ARGON’S PHOTOIONISATION. Petrov’s Table 2 total at the 2P1/2 threshold, sigma_tot^0 (tot_Ar_*, at the photon energies 2.6545, 2.6349, 2.6092 eV, the same thresholds as here): 4p’[3/2]1 (2p4) 10.82 Mb, 4p’[3/2]2 (2p3) 10.71, 4p’[1/2]1 (2p2) 9.95. Baig / Petrov: 34 / 10.82 = 3.14 +- 0.46, 31 / 10.71 = 2.89 +- 0.47, 28 / 9.95 = 2.81 +- 0.40 (Baig’s +- only); the differences are 4.6, 4.1 and 4.5 times Baig’s +-. Petrov’s 2P3/2-ion channel alone at threshold is 1.54, 1.79 and 2.31 Mb, and the 2P1/2 channel at Delta_FS above it 8.80, 8.80 and 7.72 Mb (s32_*, s12_*); Baig exceeds every one. The level ordering agrees ([3/2]1 >= [3/2]2 > [1/2]1 in both). The paper itself had nothing to compare with (p. 5) and quotes Samson and Stolte’s ground-state cross section at the same threshold, ~36 Mb. This is the only measured absolute photoionisation of argon 4p levels in the library; it is at threshold (omega_1/2 = 0), not at OEP 8’s drive (omega_1/2 = 3.7-4.3 eV), and for three J = 1, 2 primed levels, none of OEP 8’s: nothing is derived for the drive, and the doubts above (beam area, discharge threshold) are not resolved.
NOT TAKEN. Table II (p. 6): the oscillator strengths of the autoionising transitions 4p’[3/2]2 -> nd’[5/2]3 (n = 20-48), 4p’[3/2]1 -> nd’[5/2]2 (n = 18-52) and 4p’[1/2]1 -> nd’[3/2]2 (n = 18-50), 1e-4 to 4e-5, and their wavelengths: oscillator_strength holds the absorption f of a transition with no lower-level parameter, and every dataset under it is from the ground state; these are excited-state f values of autoionising resonances, Fano-generalised (f-bar, Eq. 5), calibrated on the cross sections above, ‘maximum uncertainty ... about 20%’ (p. 8), with larger errors for the low n (p. 8). Table II’s wavelength columns 1 and 2 are swapped with respect to their headings: with Table I’s term energies and NIST’s 4p’ energies, 4p’[3/2]1 -> 15d’[5/2]2 is 478.52 nm and 4p’[3/2]2 -> 15d’[5/2]3 is 482.09 nm (vacuum), printed under the opposite headings (the same at n = 30: 469.82 and 473.33); the f columns follow the headings (column 1 starts at n = 20 as Fig. 2a’s [5/2]3 series), and the headings omit the prime on 4p. Table I (term energies of ns’ and nd’ levels, n = 9-52, +-0.2 cm-1): no level quantity for autoionising Rydberg levels is needed by OEP 8. Fig. 4’s Fano parameters (15d’[5/2]2: E0 = 128029.38 cm-1, Gamma = 1.44 cm-1, q = 27), the power-law exponents of the f values (2.88, 2.92, 2.34), the lifetimes quoted for the 4p’ levels (29, 26, 26 ns, p. 3, no reference) and for 4s[3/2]1, 4s’[1/2]1 (8.6, 2.15 ns, Lawrence), and Faust and McFarlane’s relative line strengths: no quantity, or quoted. No two-photon data.
Recorded bibliographic identity status: VALIDATED_WITH_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents.
Datasets#
baig_2008/pi_pp32_1#
{
"id": "pi_pp32_1",
"material": "Ar",
"table": "text",
"quantity": "excited_state_photoionization_cross_section",
"unit": "Mb",
"abscissa_unit": "nm",
"wavelength_medium": "vacuum",
"use": "primary",
"uncertainty": {
"column": true,
"level": "not stated"
},
"parameters": {
"initial_level": "Ar 4p'[3/2]1 = 3s2.3p5.(2P*<1/2>).4p 2[3/2] J = 1 (NIST, 107131.7086 cm-1); Paschen 2p4",
"method": "saturation of the two-step photoionisation signal (optogalvanic, dc discharge), at the 2P1/2 threshold"
}
}
1 inline points in the source record.
p. 5 (and the abstract): ‘the photoionization cross section at the ionization threshold as 34 +- 5 Mb’ from 4p’[3/2]1, ionising laser at 467.1 nm, the 3p5 2P1/2 threshold (vacuum wavelength, record notes), by the saturation of the ion signal (Fig. 3). petrov_2011 (calculated) gives 10.82 Mb here: ratio 3.14.
baig_2008/pi_pp32_2#
{
"id": "pi_pp32_2",
"material": "Ar",
"table": "text",
"quantity": "excited_state_photoionization_cross_section",
"unit": "Mb",
"abscissa_unit": "nm",
"wavelength_medium": "vacuum",
"use": "primary",
"uncertainty": {
"column": true,
"level": "not stated"
},
"parameters": {
"initial_level": "Ar 4p'[3/2]2 = 3s2.3p5.(2P*<1/2>).4p 2[3/2] J = 2 (NIST, 107289.7001 cm-1); Paschen 2p3",
"method": "saturation of the two-step photoionisation signal (optogalvanic, dc discharge), at the 2P1/2 threshold"
}
}
1 inline points in the source record.
p. 5 (and the abstract): ‘from the 3p5 4p’[3/2]2 level at 470.5 nm as 31 +- 5 Mb’, at the 3p5 2P1/2 threshold (vacuum 470.551 nm; record notes), by saturation. petrov_2011 (calculated) gives 10.71 Mb here: ratio 2.89.
baig_2008/pi_pp12_1#
{
"id": "pi_pp12_1",
"material": "Ar",
"table": "text",
"quantity": "excited_state_photoionization_cross_section",
"unit": "Mb",
"abscissa_unit": "nm",
"wavelength_medium": "vacuum",
"use": "primary",
"uncertainty": {
"column": true,
"level": "not stated"
},
"parameters": {
"initial_level": "Ar 4p'[1/2]1 = 3s2.3p5.(2P*<1/2>).4p 2[1/2] J = 1 (NIST, 107496.4166 cm-1); Paschen 2p2",
"method": "saturation of the two-step photoionisation signal (optogalvanic, dc discharge), at the 2P1/2 threshold"
}
}
1 inline points in the source record.
p. 5 (and the abstract): ‘from the 3p5 4p’[1/2]1 level at 475.17 nm ionizing laser wavelengths as 28 +- 4 Mb’, at the 3p5 2P1/2 threshold (vacuum wavelength, record notes), by saturation. petrov_2011 (calculated) gives 9.95 Mb here: ratio 2.81.
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.