shaw_1993 ========= M\. J\. Shaw, C\. J\. Hooker and D\. C\. Wilson, Opt\. Commun\. 103, 153 \(1993\) `Source record `__ · :doc:`Catalogue ` · :doc:`Review register ` DOI: `10\.1016/0030\-4018\(93\)90657\-q `__ **Source kind:** measurement **Recorded technique:** Self\-phase modulation of about 10 ps pulses at 248\.6 nm \(tripled 746 nm Ti\:sapphire oscillator pulses amplified in a dye amplifier and a double\-passed KrF discharge amplifier to 2 mJ, 180 MW, 8 Hz\) focused by a 2 m lens into a 3 m pressure cell; spectra on an echelle spectrometer \(0\.2 cm^\-1\) against pressure \(Baratron gauge\) in both directions; the B integral of each spectrum fitted with a modelled asymmetric pulse shape \(sech^2 oscillator pulse cubed and passed through a saturated amplifier, Eqs\. 9\-11\); relative n2 from the slopes of B against pressure \(Eq\. 8, Fig\. 4\)\. **Materials in structured entries:** Ar, CH4, He, N2, Ne, O2 **Dataset quantities:** nonlinear\_index\_ratio **Contents:** 6 datasets; 0 formulas. Curation notes -------------- Defining equations \(p\. 2\)\: n = n0 \+ n2 \ = n0 \+ Gamma I \(Eq\. 1\), 'I is the intensity \(watt/cm^2\) and Gamma = 4\.2 x 10^\-3 \(n2/n0\) \(n2 in e\.s\.u\.\)'; B\(t\) = k Gamma int\_0^L I dl \(Eqs\. 4\-5\); B = B1 \+ alpha gamma P with alpha = k int I dl and gamma = Gamma/P, 'n2 is usually specified at a pressure of 760 Torr' \(p\. 3\)\. Gamma is the single\-beam \(self\) coefficient of SPM\. The absolute scale needs int I dl, estimated as 6\.8 \+\- 2\.4 TW/cm \(from 4\.5, 7\.6 and 9\.2 TW/cm by three assumptions, p\. 3\), so the absolute values are uncertain by \+\-33 %; the ratios to air are better than 10 % \(Conclusion, p\. 7\-8\)\. Only the ratios \(Table 1\) are for curated gases; the only absolute value is for air\: 'n2 for air at 248 nm, 760 Torr and 300 K of 2\.9 \+\- 1\.0 x 10^\-16 esu' \(p\. 5\), not a curated species\. B1 = 1\.3 with the cell evacuated \(window and lens material\)\. Table 1 \('Relative values of nonlinear refractive index at 248 nm\. Errors shown are calculated from the standard errors in the slopes of the fitted lines'; tbl\_d1f5f8c27975, image checked\)\: air 1\.00, N2 0\.62 \+\- 0\.03, O2 2\.50 \+\- 0\.25, Ar 0\.24 \+\- 0\.01, CH4 0\.94 \+\- 0\.07, Ne 0\.005 \+\- 0\.001, He \-0\.002 \+\- 0\.001\. Extracted as nonlinear\_index\_ratio against 'air' \(reference\_material = air, not a curated species; same pressure, 760 Torr and 300 K for the absolute value\)\. The uncertainties are standard errors of slopes \(1 sigma\)\. \- O2 is not measured\: 'calculated using the results obtained for air, nitrogen and argon, assuming that oxygen makes a 21 % contribution to the total nonlinear index of air while nitrogen contributes 78 % and argon 1 %' \(p\. 5\)\. Check\: \(1 \- 0\.78 x 0\.62 \- 0\.01 x 0\.24\)/0\.21 = 2\.45 against 2\.50 printed \(2 %, presumably unrounded slopes\)\. \- CH4\: stimulated Raman scattering above about 250 Torr raised the slope; only the data below 250 Torr were used \(p\. 5\)\. \- Ne \(just observable at 7000 Torr\) and He \(no broadening; a slight narrowing, 50 spectra\)\: the authors write 'It seems plausible that our values for helium and probably also neon were affected by ionization in the focal region' \(p\. 8\), with an MPI estimate giving B of about \-0\.1 \(p\. 7\)\: both excluded\. \- Molecules\: 'at our pulselength of 10 ps there is some reduction of the susceptibility of the molecular gases due to the freezing out of the nuclear motions' \(p\. 6; rovibrational response times 1\-2 ps estimated\)\. Recorded as part = total \(the nuclear response is largely adiabatic at 10 ps\), with that caveat\. The ratio N2/Ar disagrees with Hellwarth et al\.'s calculation \(p\. 6\)\. Wavelength\: 248\.6 nm \(the KrF gain peak, p\. 3; medium not stated\)\. Pulse\: 'about 10 ps' \(streak camera\), modelled as an asymmetric pulse of about 11 ps FWHM \(p\. 4\)\. **Recorded bibliographic identity status:** VALIDATED\_WITH\_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents. Datasets -------- shaw\_1993/ratio\_N2 ~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "ratio_N2", "material": "N2", "file": "N2/shaw_1993__ratio_N2.csv", "table": "tbl_d1f5f8c27975", "quantity": "nonlinear_index_ratio", "abscissa_unit": "nm", "use": "primary", "uncertainty": { "column": true, "level": "1 sigma" }, "parameters": { "reference_material": "air", "part": "total", "pulse_fs": 10000 } } Table 1\: n2\(N2\)/n2\(air\) at 248\.6 nm, SPM of 10 ps pulses, slope standard error\. shaw\_1993/ratio\_O2 ~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "ratio_O2", "material": "O2", "file": "O2/shaw_1993__ratio_O2.csv", "table": "tbl_d1f5f8c27975", "quantity": "nonlinear_index_ratio", "abscissa_unit": "nm", "use": "check", "uncertainty": { "column": true, "level": "1 sigma" }, "parameters": { "reference_material": "air", "part": "total", "pulse_fs": 10000 } } Table 1\: n2\(O2\)/n2\(air\), not measured but derived from air, N2 and Ar with volume fractions 0\.21/0\.78/0\.01 \(p\. 5\); marked check because it is a combination of the other ratios\. shaw\_1993/ratio\_Ar ~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "ratio_Ar", "material": "Ar", "file": "Ar/shaw_1993__ratio_Ar.csv", "table": "tbl_d1f5f8c27975", "quantity": "nonlinear_index_ratio", "abscissa_unit": "nm", "use": "primary", "uncertainty": { "column": true, "level": "1 sigma" }, "parameters": { "reference_material": "air", "part": "electronic", "pulse_fs": 10000 } } Table 1\: n2\(Ar\)/n2\(air\) at 248\.6 nm \(numerator electronic, reference air total\), up to 3500 Torr of Ar\. shaw\_1993/ratio\_CH4 ~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "ratio_CH4", "material": "CH4", "file": "CH4/shaw_1993__ratio_CH4.csv", "table": "tbl_d1f5f8c27975", "quantity": "nonlinear_index_ratio", "abscissa_unit": "nm", "use": "primary", "uncertainty": { "column": true, "level": "1 sigma" }, "parameters": { "reference_material": "air", "part": "total", "pulse_fs": 10000 } } Table 1\: n2\(CH4\)/n2\(air\) at 248\.6 nm from the slope below 250 Torr \(SRS above\)\. shaw\_1993/ratio\_Ne ~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "ratio_Ne", "material": "Ne", "file": "Ne/shaw_1993__ratio_Ne.csv", "table": "tbl_d1f5f8c27975", "quantity": "nonlinear_index_ratio", "abscissa_unit": "nm", "use": "excluded", "uncertainty": { "column": true, "level": "1 sigma" }, "parameters": { "reference_material": "air", "part": "electronic", "pulse_fs": 10000 } } Table 1\: n2\(Ne\)/n2\(air\)\. Excluded\: the authors think neon 'probably also' affected by ionisation in the focus \(p\. 8\); broadening only just observable at 7000 Torr\. shaw\_1993/ratio\_He ~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "ratio_He", "material": "He", "file": "He/shaw_1993__ratio_He.csv", "table": "tbl_d1f5f8c27975", "quantity": "nonlinear_index_ratio", "abscissa_unit": "nm", "use": "excluded", "uncertainty": { "column": true, "level": "1 sigma" }, "parameters": { "reference_material": "air", "part": "electronic", "pulse_fs": 10000 } } Table 1\: n2\(He\)/n2\(air\) = \-0\.002 \+\- 0\.001, a slight spectral narrowing; excluded\: the authors attribute it to free electrons from multiphoton ionisation in the focus \(p\. 7\-8\)\. An upper limit on He's n2 at best\. 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 ` for the checks and decisions.