loriot_2008
===========

V\. Loriot, E\. Hertz, B\. Lavorel and O\. Faucher, "Field\-free molecular alignment for measuring ionization probability", J\. Phys\. B\: At\. Mol\. Opt\. Phys\. 41, 015604 \(2008\)

`Source record <https://github.com/LupoLab/optmat/blob/main/src/optmat/data/sources/loriot_2008.toml>`__ · :doc:`Catalogue </the-data/sources>` · :doc:`Review register </register>`

DOI: `10\.1088/0953\-4075/41/1/015604 <https://doi.org/10.1088/0953-4075/41/1/015604>`__

**Source kind:** measurement

**Recorded technique:** All\-optical 'cross\-defocusing' pump\-probe measurement \(pp\. 1\-3, Fig\. 1\)\: the pump aligns the molecules and ionises the gas; the refractive\-index gradients of the alignment, Delta n\_R, and of the plasma, Delta n\_p = \-n\_e / \(2 n\_cr\) \(Eq\. 8, n\_cr = 1\.75 x 10^21 cm^\-3 'the critical density at 800 nm'\), defocus a delayed probe, whose defocused light \(behind a mask\) is detected by a photomultiplier\. The signal, S\(t\) ~ I\_pr\(t\) \(x\) \[\<cos^2 theta\>\(r = 0, t\) \- 1/3 \+ F\]^2 \(Eq\. 11\), is fitted with the computed alignment \<cos^2 theta\>\(t\) and F free; F gives the ionisation probability at the beam centre, P\_ion\(I\_0\) = \-n\_cr Delta alpha F\(I\_0\) / \(eps0 N\_L\) \(Eq\. 12\), so the plasma is calibrated by the molecules' alignment \('the cross\-defocusing signal depends on the degree of alignment at the beam centre r = 0 exposed to the peak intensity I\_0 without any further spatial averaging', p\. 3\)\. Delta alpha\(N2\) = 8\.24 x 10^\-41 C m2 V^\-1 \(ref\. 28\); N\_L = 7\.5 \+\- 0\.5 from the F values at several intensities \(p\. 3, from ref\. \[24\]\)\. For a molecule and its companion atom, whose signal is the plasma's alone \(Eq\. 15\), 'Experiments are performed in the same experimental conditions for the atom and the reference molecule' and the ratio is R = Delta n\_p0^mol / Delta n\_p0^atom \(Eq\. 16\), at high intensity 'the square root of the ratio of the baselines measured in each species' \(p\. 4\), the permanent alignment accounted for where not negligible \(p\. 5\)\. Laser \(p\. 1\)\: 'a Ti\:sapphire oscillator with a chirped pulse amplification stage providing 100 fs pulse duration with a maximum energy of 1 mJ at a 1 kHz repetition rate'; pump energy set with a half\-wave plate and a polariser; pump and probe focused by one f = 30 cm lens, crossing at about 4 degrees, 'the measured waist at the focus is 40 um'; static cell, 0\.1 to 1 bar, room temperature\. Probe polarisation parallel or perpendicular to the pump's \(Eq\. 13\-14\)\.

**Materials in structured entries:** N2

**Dataset quantities:** ionization\_yield, ionization\_yield\_ratio

**Contents:** 4 datasets; 0 formulas.

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

J\. Phys\. B 41 \(2008\) 015604 \(6 pp\.\)\. The PDF's page 1 is the publisher's cover sheet \('To cite this article\: V Loriot et al 2008 J\. Phys\. B\: At\. Mol\. Opt\. Phys\. 41 015604'\)\: article page n is PDF page n \+ 1\. Identity checked on the article's first page \(PDF p\. 2\) on 2026\-10\-01\: 'Field\-free molecular alignment for measuring ionization probability', V Loriot, E Hertz, B Lavorel and O Faucher, Institut Carnot de Bourgogne, Dijon; 'Received 24 September 2007, in final form 30 October 2007; Published 19 December 2007' \(online 2007, the issue 2008\: the id uses 2008, the library directory 2007\)\.

DETECTION \(detection\_correction = "optical"\)\. No ion detector\: the electrons are measured through the plasma's refractive index, calibrated by the molecular alignment; 'the present technique is experimentally simple and does not require any precise calibration of the overall detection efficiency encountered in ion mass or photoelectron spectroscopy' \(p\. 5\)\. What is measured is the electron density, i\.e\. all ionisation; 'Only single ionization is considered in the following since other double ionization or dissociation processes are orders of magnitude lower \[26, 30\]' \(p\. 3\)\.

PROBABILITY AT THE PEAK, NOT VOLUME\-AVERAGED\. P\_ion is that 'at the beam centre r = 0 exposed to the peak intensity I\_0' \(pp\. 3, 5\)\: the model takes the alignment linear in the intensity \(Gaussian profile, Eqs\. 2\-4\) and the plasma ~ I^N\_L \(Eqs\. 7, 9\), with parabolic approximations of both gradients\. 'Above I\_0 ~ 100 TW cm^\-2, the initial assumption of a linear dependence of \<cos^2 theta\> with the intensity is no longer fulfilled and the ionization probability appears underestimated' \(p\. 4\)\.

INTENSITY\. How I\_0 was obtained is not described beyond the 40 um waist, the 100 fs duration and the energy set by the wave plate; no uncertainty of it is stated\. The semi\-empirical curve of Fig\. 4 \(Talebpour et al\., ref\. 31, in the form of ref\. 32\) 'is in good agreement with our results\. It should be noted that the intensity of the theoretical curve has been multiplied by a factor of only 1\.2 corresponding to a rather minor uncertainty in the estimation of the intensity of both experiments' \(p\. 4\)\: a shift applied to the theory to match, not an error bar of these intensities\. The polarisation of the pump is linear\: implied by 'the pump polarization axis' along which the molecules align and the polariser in the pump arm \(p\. 1\-2\); not stated in those words\.

UNCERTAINTY\. F is fitted 'with its standard deviation \(reflecting the accuracy\)' and P\_ion deduced 'with its standard deviation' \(p\. 3\), but Fig\. 4 draws no bars; its caption\: 'Region \(A\) denotes the intensity range in which the standard deviation for P\_ion is less than 10% using parallel polarizations\. For perpendicular polarizations, it includes region \(B\) in addition to region \(A\)'; region \(A\) is 'from about 38 TW cm^\-2 to 100 TW cm^\-2' \(p\. 4\)\. Read from the drawing, the lines bounding the regions are at 30\.08, 37\.95 and 99\.96 TW/cm2\. Outside them the standard deviation exceeds 10 % by an amount not stated\: the parallel points at 36\.1 and 110\.7 TW/cm2 \(rows 1 and 12\) and the perpendicular point at 28\.0 TW/cm2 \(row 1\)\.

THE O2\:Xe RATIO is not a value\: 'The signal produced by Xe is much larger than the one of O2 and the ratio O2\+\:Xe\+ has been estimated lower than 0\.2 for I\_0 \< 40 TW cm^\-2' \(pp\. 4\-5\)\: an upper bound, not recorded as a dataset \(the format records values, and a bound is not one; as schrotter\_1979's '\<0\.01'\)\.

EXTRACTED \(2026\-10\-01\) by tools/extract/loriot\_2008\.py from the vector drawings of Figs\. 4 and 7, whose docstring describes the reading\. The tick labels are drawn as glyph outlines, so their printed values are written in the script; the ticks lie on the fitted scales within 0\.042 pt \(Fig\. 4\) and 0\.022 pt \(Fig\. 7\)\.

CHECKS\. \(1\) The lines of regions \(A\) and \(B\) read on the calibrated axis, 37\.95 and 99\.96 TW/cm2, against the text's 'from about 38 TW cm^\-2 to 100 TW cm^\-2'\. \(2\) The slope of log P\_ion against log I\_0 of the 10 parallel points inside region \(A\) is 6\.99, against the N\_L = 7\.5 \+\- 0\.5 the paper takes from its fitted F \(p\. 3, ref\. \[24\]\)\. \(3\) The seven N2\:Ar points of Fig\. 7 \(44\.2\-88\.0 TW/cm2\) have a mean of 0\.811 and a standard deviation of 0\.070, against the text's '0\.8 \+\- 0\.1' \(p\. 5\)\. \(4\) Fig\. 7 redraws ten of DeWitt et al\.'s N2\:Ar points \(blue squares, 'DeWitt et al \[35\] \(790 nm, 100 fs\)'\)\: each matches a point read from DeWitt et al\.'s own Fig\. 2 \(dewitt\_2001\) within 0\.21 % in intensity and 0\.005 in the ratio \(compare\_dewitt in the script\), so both readings, and the two papers' intensity scales for those data, agree\. \(5\) The extracted points drawn on the rendered pages and inspected on 2026\-10\-01\: every circle and triangle captured once, Guo et al\.'s triangles and DeWitt et al\.'s squares not taken\. \(6\) Where the parallel and perpendicular points overlap \(38\-44 TW/cm2\) they agree\: 8\.93e\-6 at 38\.8 and 8\.19e\-6 at 37\.9 TW/cm2\.

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

Datasets
--------

loriot\_2008/fig4\_parallel
~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. code-block:: text

   {
     "id": "fig4_parallel",
     "material": "N2",
     "file": "N2/loriot_2008__fig4_parallel.csv",
     "table": "fig_bea52e231748",
     "digitised": "vector",
     "quantity": "ionization_yield",
     "unit": "1",
     "abscissa": "intensity",
     "abscissa_unit": "W/cm2",
     "use": "reproduced",
     "reproduced_from": [
       "V. Loriot, E. Hertz, A. Rouzee, B. Sinardet, B. Lavorel and O. Faucher, Opt. Lett. 31, 2897 (2006)"
     ],
     "uncertainty": {
       "relative": 0.1,
       "level": "1 sigma"
     },
     "parameters": {
       "wavelength_nm": 800,
       "pulse_fs": 100,
       "pulse_fs_definition": "as printed ('100 fs pulse duration'); the measure is not stated",
       "polarization": "linear",
       "probe_polarization": "parallel to the pump's",
       "waist_um": 40,
       "measure": "probability at the beam centre (peak intensity), all-optical (cross-defocusing), calibrated by the molecular alignment; not volume-averaged"
     }
   }

Fig\. 4, article p\. 4, full circles\: 'Ionization probability of N2 with \(filled circle\) parallel \(from our previous work \[24\]\)' pump and probe polarisation; the probability at the beam centre against the peak intensity, 12 points, 3\.61e13\-1\.107e14 W/cm2, P 3\.46e\-6 to 5\.84e\-3, read from the vector drawing \(TW/cm2 on the figure\)\. Reproduced from Loriot et al\. 2006 \(ref\. \[24\], not in the library\)\. 10 %\: 'Region \(A\) \[37\.95\-99\.96 TW/cm2 on the drawing\] denotes the intensity range in which the standard deviation for P\_ion is less than 10% using parallel polarizations' \(the caption\)\: an upper bound inside region \(A\), exceeded by an unstated amount at rows 1 \(36\.1 TW/cm2\) and 12 \(110\.7 TW/cm2\); above 100 TW/cm2 'the ionization probability appears underestimated' \(p\. 4\)\. The digitising \(0\.04 pt of 24\.9 pt per decade, 0\.4 %\) is negligible\. Intensity\: no calibration or uncertainty stated \(the record's notes; the theory's x1\.2 is not an error bar\)\.

loriot\_2008/fig4\_perpendicular
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. code-block:: text

   {
     "id": "fig4_perpendicular",
     "material": "N2",
     "file": "N2/loriot_2008__fig4_perpendicular.csv",
     "table": "fig_bea52e231748",
     "digitised": "vector",
     "quantity": "ionization_yield",
     "unit": "1",
     "abscissa": "intensity",
     "abscissa_unit": "W/cm2",
     "use": "check",
     "uncertainty": {
       "relative": 0.103,
       "level": "1 sigma"
     },
     "parameters": {
       "wavelength_nm": 800,
       "pulse_fs": 100,
       "pulse_fs_definition": "as printed ('100 fs pulse duration'); the measure is not stated",
       "polarization": "linear",
       "probe_polarization": "perpendicular to the pump's",
       "waist_um": 40,
       "measure": "probability at the beam centre (peak intensity), all-optical (cross-defocusing), calibrated by the molecular alignment; not volume-averaged"
     }
   }

Fig\. 4, article p\. 4, blue triangles\: 'perpendicular pump and probe polarization', this paper's measurement \(p\. 4\: 'The ionization probability is extracted with this configuration and values are displayed in figure 4 as triangles'\); the probability at the beam centre against the peak intensity, 6 points, 2\.80e13\-4\.42e13 W/cm2, P 7\.63e\-7 to 1\.54e\-5, read from the vector drawing\. 10 %\: the standard deviation is under 10 % in regions \(A\) and \(B\) \(30\.08\-99\.96 TW/cm2 on the drawing; the caption\), exceeded by an unstated amount at row 1 \(28\.0 TW/cm2\); combined with 2\.4 %, the digitising\: the triangle's centre is taken at the middle of its height, its centroid lies 0\.51 pt lower \(4\.7 % on 24\.9 pt per decade\), half of which is taken as the uncertainty\. Intensity\: no calibration or uncertainty stated\.

loriot\_2008/fig7\_N2\_Ar
~~~~~~~~~~~~~~~~~~~~~~~~~

.. code-block:: text

   {
     "id": "fig7_N2_Ar",
     "material": "N2",
     "file": "N2/loriot_2008__fig7_N2_Ar.csv",
     "table": "fig_0f8df2057eca",
     "digitised": "vector",
     "quantity": "ionization_yield_ratio",
     "unit": "1",
     "abscissa": "intensity",
     "abscissa_unit": "W/cm2",
     "use": "check",
     "uncertainty": {
       "absolute": 0.002,
       "level": "not stated"
     },
     "parameters": {
       "companion": "Ar",
       "wavelength_nm": 800,
       "pulse_fs": 100,
       "pulse_fs_definition": "as printed ('800 nm, 100 fs'); the measure is not stated",
       "polarization": "linear",
       "detection_correction": "optical",
       "detection_correction_note": "no ion detector: electron densities from the plasma's refractive index, calibrated by the molecular alignment",
       "waist_um": 40,
       "mixture": false
     }
   }

Fig\. 7, article p\. 5, black circles\: 'Ionization ratio N2\+\:Ar\+ from the present technique \(800 nm, 100 fs\)', 7 points, 4\.42e13\-8\.80e13 W/cm2, ratio 0\.716\-0\.891, read from the vector drawing \(TW/cm2 on the figure\)\. The ratio of the plasma index changes \(electron densities\) at the beam centre, molecule over atom, measured separately in the same conditions \(Eq\. 16\), not in a mixture; all\-optical, no detector efficiency\. Which probe polarisation is not stated\. No bars are drawn; the text gives the mean, '0\.8 \+\- 0\.1' \(text\_N2\_Ar; these points' mean 0\.811, sd 0\.070\)\. 0\.002\: the digitising \(0\.02 pt of 30\.2 pt per 0\.5\)\.

loriot\_2008/text\_N2\_Ar
~~~~~~~~~~~~~~~~~~~~~~~~~

.. code-block:: text

   {
     "id": "text_N2_Ar",
     "material": "N2",
     "table": "text",
     "quantity": "ionization_yield_ratio",
     "unit": "1",
     "abscissa": "label",
     "use": "check",
     "uncertainty": {
       "column": true,
       "level": "not stated"
     },
     "parameters": {
       "companion": "Ar",
       "wavelength_nm": 800,
       "pulse_fs": 100,
       "polarization": "linear",
       "detection_correction": "optical",
       "intensity_range": "not printed with the number; Fig. 7's points, 4.4e13-8.8e13 W/cm2",
       "mixture": false
     }
   }

1 inline points in the source record.

Article p\. 5\: 'The experimental ionization ratio N2\+\:Ar\+ depicted in figure 7 yields a value 0\.8 \+\- 0\.1', 'closer to the ratio reported by Guo et al' than to DeWitt et al\.'s; 'the observation of a constant ratio as the intensity rises is a good indication of insignificant dynamical intra\-pulse alignment'\. The intensity range is not printed with the number\: that of Fig\. 7's points, 44\-88 TW/cm2\. The level of \+\-0\.1 is not stated\. MO\-ADK alignment estimate\: the intra\-pulse alignment changes the rate by 'less than 20%' at T = 300 K in this range \(p\. 5\)\.

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.