geints_2025 =========== Yu\. E\. Geints, V\. O\. Kompanets and S\. V\. Chekalin, Opt\. Commun\. 596, 132584 \(2025\) `Source record `__ · :doc:`Catalogue ` · :doc:`Review register ` DOI: `10\.1016/j\.optcom\.2025\.132584 `__ **Source kind:** measurement **Recorded technique:** Self\-focusing distance of collimated \(4 mm\) 800 nm Ti\:sapphire pulses \(45 fs, 48 fs after the entrance window, taken as 50 fs; chirped to 100\-500 fs with the compressor; up to 3 mJ, about 60 GW; 20 Hz\) in a 315 cm polycarbonate cell of Ar, N2 or CO2 \(99\.995 %\) at 1\-11 bar; the filament start z\_SF located with a movable screen from the plasma spot and the onset of supercontinuum; n2 from Marburger's law z\_SF ~ \(P0/P\_c\)^\-k with k = 0\.5 and P\_c = 3\.79 lambda^2 / \(8 pi n0 n2\), relative to a reference\. **Materials in structured entries:** Ar, CO2, N2 **Dataset quantities:** nonlinear\_index **Contents:** 7 datasets; 0 formulas. Curation notes -------------- Defining equations \(p\. 2\-3\)\. n\(E\) = n0 \+ n2 \|E\|^2 \(p\. 2; the values are in m^2/W, so \|E\|^2 is the intensity\: coefficient = self, the single\-beam index of self\-focusing\)\. P\_c = 3\.79 lambda^2 / \(8 pi n0 n2\) \(Eq\. 2\); z\_SF ~ L\_R\* / eta^k, eta = P0/P\_c \(Eq\. 1\); linear pressure scaling n2\(mu\) = mu n2^0, mu = p/p0 \(Eq\. 3\); n2^0\(t\) = n\_K^0 \[1 \+ f\_R h\_R\(t\)\] with a damped\-oscillator Raman response \(Eqs\. 6\-7; for air Omega\_R = 16 THz, tau1 = 70 fs\); n2^0\(tau\_p\) = n2^sh \[1 \+ Delta n\_R\(tau\_p\)\] \(Eq\. 8\), with Delta n\_R from the ratio of z\_SF of chirped \(long\) and short pulses at equal eta0 \(Eq\. 10\), and the pressure dependence of n2^sh from n2^sh\(p\)/n2^sh\(p0\) = \(1/mu\) \[z\_SF^sh\(p0\)/z\_SF^sh\(p\)\]^\(1/k\) \(Eq\. 11\), fitted with z\_SF = L\_R\* \[eta mu a \(1 \+ b mu\)\]^\-0\.5 \(Eq\. 12, L\_R\* = 2\.68 m\)\. Calibration\: absolute values rest on Wahlstrand et al\. \(Phys\. Rev\. A 85, 043820 \(2012\), ref\. 25\)\: 'The experimental data from Ref\. \[25\] were used as a benchmark for the purely Kerr response of nitrogen and argon' \(p\. 7\), n2^sh = 7\.4 \(N2\) and 9\.7 x 10^\-24 m^2/W \(Ar\) \(p\. 6\)\. For CO2 at 1 bar\: 'in the case of the SP limit, the nonlinear response of CO2 is most similar in magnitude to that of argon\. Consequently, we can estimate that the value of n2^sh\(CO2\) = 10^\-23 m^2/W best suits the experimental data' \(p\. 6\); Table 1 prints 10\.0 \+\- 1\.1 \(this work\)\. So the CO2 value is in effect a ratio to Wahlstrand's Ar, from z\_SF comparisons\. Check of the LP column\: LP = SP x \(1 \+ Delta n\_R\) with the paper's Delta n\_R\(1 bar\) at the longest pulse, 0\.92 \(N2\) and 4\.4 \(CO2\) \(p\. 7\)\: 7\.4 x 1\.92 = 14\.2 and 10\.0 x 5\.4 = 54\.0, against 14\.1 and 54\.1 printed\. Table 1 \('Optical Kerr nonlinearity \(n2 x 10^24 m^2/W\) of compressed gases at lambda = 800 nm'; SP tau\_p = 50 fs, LP tau\_p = 250\.\.\.500 fs; tbl\_2c05f4da79d1, JSON cells equal to the image\)\: Ar SP 9\.7 \+\- 1\.5 \(a, ref\. 25\), 18\.9 \+\- 1\.8, 26\.2 \+\- 2\.5; N2 SP 7\.4 \+\- 0\.9 \(a\), 14\.4 \+\- 1\.6, 20\.1 \+\- 2\.2 and LP 14\.1 \+\- 1\.5, 36\.0 \+\- 3\.9, 74\.7 \+\- 8\.5; CO2 SP 10\.0 \+\- 1\.1, 19\.6 \+\- 2\.0, 27\.3 \+\- 2\.6 and LP 54\.1 \+\- 3\.8, 121\.5 \+\- 9\.3, 333\.1 \+\- 10\.4 \(1, 5, 11 bar\)\. Geints quote Wahlstrand's Ar value as 9\.7 \+\- 1\.5; Wahlstrand et al\. 2012 \(Table I, image\) print 9\.7 \+\- 1\.2 \(and N2 7\.4 \+\- 0\.9\); Geints label them '1 bar', Wahlstrand's are at 1 atm\. The 5 and 11 bar values are excluded rows\: they are not n2 at 5 or 11 bar \(linear scaling would give 48\.5 and 107 for Ar\) but the pressure\-normalised effective coefficient of Eq\. \(11\) \(the 1/mu factor\), and its rise with pressure is attributed by the authors to beam aberration and modulation instability during self\-focusing, not to the gas \(p\. 6, Conclusion\)\. The interpretation of these columns as per\-1\-bar values is this record's reading of Eq\. \(11\); the paper does not state it\. Parts\. Ar\: electronic\. N2 and CO2\: the SP \(50 fs\) value still contains part of the rotational response \(the paper's Delta n\_R is measured relative to it, p\. 6\-7\) and the LP values contain much more\: both part = instantaneous \(pulse\-dependent mixtures\)\. Uncertainty\: the \+\- of Table 1 \(regression standard errors below 10 % for SP, p\. 5; level not stated\)\. State\: '1 bar' with no temperature\: 100000 Pa and 293\.15 K assumed\. Wavelength 800 nm \(central\)\. **Recorded bibliographic identity status:** VALIDATED. This concerns identification of the source; it does not establish the scientific correctness of its contents. Datasets -------- geints\_2025/sp\_CO2 ~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "sp_CO2", "material": "CO2", "file": "CO2/geints_2025__sp_CO2.csv", "table": "tbl_2c05f4da79d1", "quantity": "nonlinear_index", "unit": "m2/W", "scale": 1e-24, "abscissa_unit": "nm", "state": { "pressure_pa": 100000.0, "temperature_k": 293.15 }, "use": "primary", "excluded_rows": { "sp_5bar": "Measured at 5 bar; the pressure-normalised effective value of Eq. (11), whose rise with pressure the authors attribute to beam aberration (p. 6).", "sp_11bar": "Measured at 11 bar; pressure-normalised effective value, aberration-affected (p. 6)." }, "uncertainty": { "column": true, "level": "not stated" }, "parameters": { "part": "instantaneous", "coefficient": "self", "pulse_fs": 50 } } Table 1, SP \(50 fs\) column, 1 bar\: 10\.0 \+\- 1\.1 x 10^\-24 m^2/W, 'for the first time' for CO2 at 800 nm \(abstract\); in effect scaled to Wahlstrand's Ar value \(see the record's notes\)\. Contains part of the rotational response\. 293\.15 K assumed\. geints\_2025/lp\_CO2 ~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "lp_CO2", "material": "CO2", "file": "CO2/geints_2025__lp_CO2.csv", "table": "tbl_2c05f4da79d1", "quantity": "nonlinear_index", "unit": "m2/W", "scale": 1e-24, "abscissa_unit": "nm", "state": { "pressure_pa": 100000.0, "temperature_k": 293.15 }, "use": "primary", "excluded_rows": { "lp_5bar": "Measured at 5 bar; pressure-normalised effective value (Eqs. 10-11), aberration-affected.", "lp_11bar": "Measured at 11 bar; pressure-normalised effective value, aberration-affected." }, "uncertainty": { "column": true, "level": "not stated" }, "parameters": { "part": "instantaneous", "coefficient": "self", "pulse_fs": 500 } } Table 1, LP column, 1 bar\: SP x \(1 \+ Delta n\_R\) with Delta n\_R = 4\.4 for the longest \(500 fs\) chirped pulse \(p\. 7\); the rotational response of CO2 was still growing at 500 fs \(Fig\. 6a\)\. 293\.15 K assumed\. geints\_2025/lp\_N2 ~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "lp_N2", "material": "N2", "file": "N2/geints_2025__lp_N2.csv", "table": "tbl_2c05f4da79d1", "quantity": "nonlinear_index", "unit": "m2/W", "scale": 1e-24, "abscissa_unit": "nm", "state": { "pressure_pa": 100000.0, "temperature_k": 293.15 }, "use": "primary", "excluded_rows": { "lp_5bar": "Measured at 5 bar; pressure-normalised effective value (Eqs. 10-11), aberration-affected.", "lp_11bar": "Measured at 11 bar; pressure-normalised effective value, aberration-affected." }, "uncertainty": { "column": true, "level": "not stated" }, "parameters": { "part": "instantaneous", "coefficient": "self", "pulse_fs": 300 } } Table 1, LP column, 1 bar\: SP \(Wahlstrand's 7\.4\) x \(1 \+ Delta n\_R\) with Delta n\_R = 0\.92 at the longest N2 pulse \(data end at 300 fs, the response saturating at 250 fs, p\. 7\)\. The authors note their n2^sh/n2^lng = 0\.52 against Wahlstrand's 0\.23 \(p\. 7\)\. 293\.15 K assumed\. geints\_2025/sp\_N2 ~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "sp_N2", "material": "N2", "file": "N2/geints_2025__sp_N2.csv", "table": "tbl_2c05f4da79d1", "quantity": "nonlinear_index", "unit": "m2/W", "scale": 1e-24, "abscissa_unit": "nm", "state": { "pressure_pa": 100000.0, "temperature_k": 293.15 }, "use": "excluded", "uncertainty": { "column": true, "level": "not stated" }, "parameters": { "part": "instantaneous", "coefficient": "self", "pulse_fs": 50 } } Table 1, SP column at 5 and 11 bar \(the 1 bar value is Wahlstrand's, dataset wahlstrand\_2012\_N2\)\: pressure\-normalised effective values \(Eq\. 11\) relative to Wahlstrand's 1 bar value; their rise with pressure is attributed by the authors to beam aberration \(p\. 6\)\. Excluded; state is the 1 bar normalisation, not the measurement pressure\. geints\_2025/sp\_Ar ~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "sp_Ar", "material": "Ar", "file": "Ar/geints_2025__sp_Ar.csv", "table": "tbl_2c05f4da79d1", "quantity": "nonlinear_index", "unit": "m2/W", "scale": 1e-24, "abscissa_unit": "nm", "state": { "pressure_pa": 100000.0, "temperature_k": 293.15 }, "use": "excluded", "uncertainty": { "column": true, "level": "not stated" }, "parameters": { "part": "electronic", "coefficient": "self", "pulse_fs": 50 } } Table 1, SP column at 5 and 11 bar \(the 1 bar value is Wahlstrand's, dataset wahlstrand\_2012\_Ar\)\: pressure\-normalised effective values \(Eq\. 11\), aberration\-affected \(p\. 6\)\. Excluded; state is the 1 bar normalisation, not the measurement pressure\. geints\_2025/wahlstrand\_2012\_Ar ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "wahlstrand_2012_Ar", "material": "Ar", "file": "Ar/geints_2025__wahlstrand_2012_Ar.csv", "table": "tbl_2c05f4da79d1", "quantity": "nonlinear_index", "unit": "m2/W", "scale": 1e-24, "abscissa_unit": "nm", "state": { "pressure_pa": 100000.0, "temperature_k": 293.15 }, "use": "reproduced", "reproduced_from": [ "wahlstrand_2012" ], "uncertainty": { "column": true, "level": "not stated" }, "parameters": { "part": "electronic", "coefficient": "self" } } Table 1, Ar SP 1 bar, footnote a \(ref\. 25\)\: Wahlstrand et al\. 2012's 9\.7, quoted with \+\- 1\.5 \(Wahlstrand print \+\- 1\.2\) and labelled 1 bar \(Wahlstrand\: 1 atm\)\. Use the wahlstrand\_2012 record\. geints\_2025/wahlstrand\_2012\_N2 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "wahlstrand_2012_N2", "material": "N2", "file": "N2/geints_2025__wahlstrand_2012_N2.csv", "table": "tbl_2c05f4da79d1", "quantity": "nonlinear_index", "unit": "m2/W", "scale": 1e-24, "abscissa_unit": "nm", "state": { "pressure_pa": 100000.0, "temperature_k": 293.15 }, "use": "reproduced", "reproduced_from": [ "wahlstrand_2012" ], "uncertainty": { "column": true, "level": "not stated" }, "parameters": { "part": "electronic", "coefficient": "self" } } Table 1, N2 SP 1 bar, footnote a \(ref\. 25\)\: Wahlstrand et al\. 2012's electronic n2 7\.4 \+\- 0\.9, labelled 1 bar \(Wahlstrand\: 1 atm\)\. Use the wahlstrand\_2012 record\. 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.