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 <https://github.com/LupoLab/optmat/blob/main/src/optmat/data/sources/baig_2008.toml>`__ · :doc:`Catalogue </the-data/sources>` · :doc:`Review register </register>`

DOI: `10\.1103/PhysRevA\.78\.032524 <https://doi.org/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
~~~~~~~~~~~~~~~~~~~~~~

.. code-block:: text

   {
     "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
~~~~~~~~~~~~~~~~~~~~~~

.. code-block:: text

   {
     "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
~~~~~~~~~~~~~~~~~~~~~~

.. code-block:: text

   {
     "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 :doc:`review register </register>` for the checks and decisions.