palm_1998
=========

H\. Palm and F\. Merkt, "Generation of tunable coherent extreme ultraviolet radiation beyond 19 eV by resonant four\-wave mixing in argon", Appl\. Phys\. Lett\. 73, 157 \(1998\)

`Source record <https://github.com/LupoLab/optmat/blob/main/src/optmat/data/sources/palm_1998.toml>`__ · :doc:`Catalogue </the-data/sources>` · :doc:`Review register </register>`

DOI: `10\.1063/1\.121741 <https://doi.org/10.1063/1.121741>`__

**Source kind:** measurement

**Recorded technique:** Two\-photon\-resonant sum\-frequency four\-wave mixing nu\_XUV = 2 nu\_1 \+ nu\_2 in a pulsed argon jet \(2\-5 bar stagnation\), nu\_1 on the Ar 3p5 4p\[5/2\]2 \<\- 3p6 two\-photon resonance at 189\.3 nm \(the sum of a frequency\-doubled dye laser at 230\.4 nm and the 1064\.55 nm Nd\:YAG fundamental in BBO\), nu\_2 a frequency\-doubled dye laser \(205\-770 nm range of the setup\); the XUV separated by a monochromator and measured with a calibrated solar\-blind photomultiplier\. Demonstrated by a PFI\-ZEKE photoelectron spectrum of O2 b 4Sigma\_g\- \(v\+ = 1\) near 18\.3 eV\.

**Materials in structured entries:** None recorded.

**Dataset quantities:** None recorded.

**Contents:** 0 datasets; 0 formulas.

Curation notes
--------------

Appl\. Phys\. Lett\. 73\(2\), 157\-159 \(13 July 1998\) = PDF pages 2\-4 \(PDF page 1 is the publisher's cover\)\. Identity checked against PDF page 2 \(journal, volume, number, date, pages, title, authors\)\.

NOTHING TAKEN\. The paper reports XUV output \(photons per pulse, a conversion efficiency of about 10^\-6, a bandwidth of 0\.1 cm^\-1\) and relative signals, not a property of argon in the vocabulary\: \(1\) The Ar 3p5 4p\[5/2\]2 two\-photon resonance, '2 nu = 105 617\.3 cm^\-1 \(Ref\. 4\)' \(p\. 157; the abstract's '105 617 cm^\-1'\), is Moore's 1949 table, reproduced \(rupper\_2004, TC\-900, quotes Minnhagen's 105 617\.2700 = NIST's, and measured 105 617\.54\(60\)\)\. The other resonances named \(Ar 4p\[1/2\]0 at 186\.8 nm and 4p'\[1/2\]0 at 184\.0 nm; Kr 5p\[1/2\]0 212\.5 nm, 5p'\[1/2\]0 202\.3 nm \(98 856 cm^\-1\), 6p\[1/2\]0 192\.7 nm\) are positions only, and agree with NIST's levels as vacuum wavelengths \(2 / 107 054\.27, 108 722\.62, 94 092\.86, 98 855\.07 and 103 761\.63 cm^\-1 = 186\.82, 183\.96, 212\.56, 202\.32 and 192\.75 nm; computed 2026\-10\-09\)\. \(2\) 'Switching to the krypton 192\.7 nm resonance under identical experimental conditions, a 45 times stronger XUV signal was found' \(p\. 159\), and the Kr 5p\[5/2\]2 resonance is 'typically, a factor of 100 weaker' than the Kr J = 0 resonances\: four\-wave\-mixing outputs, not two\-photon cross sections or transition strengths\. \(3\) The XUV energies are consistent with the resonance\: 105 617\.3 \+ 1e7/237\.5 nm = 147 722\.6 cm^\-1 = 18\.315 eV \(printed 18\.32\), \+ 1e7/219 nm = 18\.756 \(18\.76\), the third harmonic of nu\_1, 3 x 52 808\.65 cm^\-1 = 19\.642 eV \(19\.64\), and nu\_2 at the 189 nm BBO limit gives 19\.655 eV \('up to 19\.66'\)\. Not reproduced\: the krypton resonance's limit 'beyond 155 700 cm^\-1 \(19\.3 eV\)' \(p\. 157\); with the same 189 nm limit it would be 103 761\.6 \+ 52 910 = 156 672 cm^\-1 \(19\.42 eV\)\.

COMPARISON with rupper\_2004 \(TC\-900\), the same group's later source\: it uses all five Ar 3p5 4p two\-photon resonances, reached with one F2\-laser photon \(157\.63 nm\) and one tripled\-dye photon instead of two photons at 189\.3 nm, and its Table I gives relative four\-wave\-mixing efficiencies 1\.2\(2\) for 4p\[5/2\]2, 4\.0\(12\) for 4p\[1/2\]0 and 7\.5\(24\) for 4p'\[1/2\]0 \(4p\[3/2\]2 = 1\)\: the J = 0 resonances this paper expected to 'improve the conversion efficiencies at the highest energies' \(p\. 159\) are 3\.3 and 6\.3 times the 4p\[5/2\]2 resonance used here, which is consistent with, though much smaller than, the factor of about 100 between krypton's J = 2 and J = 0 resonances quoted here\. Neither paper gives a two\-photon cross section\.

TEXT\-LAYER NOTE\. The PDF's text layer \(and the library's paper\.md\) drops the mu of microjoule\: the page prints laser 1's energy at the vacuum apparatus as '10\-20 uJ' \(p\. 158, rendered page checked\), the text layer '10\-20 mJ'\. Not used\.

FURTHER TWO\-PHOTON DATA CITED\: none with values \(Refs\. 5\-7, the Kr 202\.3 nm resonance in four\-wave mixing\: H\. H\. Fielding, T\. P\. Softley and F\. Merkt, Chem\. Phys\. 155, 257 \(1991\); J\. W\. Hepburn, Chem\. Soc\. Rev\. 25, 281 \(1996\); F\. Merkt et al\., J\. Phys\. B 31, 1705 \(1998\); not in the library\)\.

**Recorded bibliographic identity status:** VALIDATED\_WITH\_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents.

Datasets
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No datasets are recorded.

Formulas
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No formulas are recorded.

Corrections
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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.