bejot_2013 ========== P\. Bejot, E\. Cormier, E\. Hertz, B\. Lavorel, J\. Kasparian, J\.\-P\. Wolf and O\. Faucher, Phys\. Rev\. Lett\. 110, 043902 \(2013\) `Source record `__ · :doc:`Catalogue ` · :doc:`Review register ` DOI: `10\.1103/physrevlett\.110\.043902 `__ **Source kind:** theory **Recorded technique:** Full 3D time\-dependent Schroedinger equation for atomic hydrogen \(B\-spline basis, velocity gauge unless stated\) in 800 nm pulses of 23\-93 fs \(24\-96 cycles\), compared with the Kerr\-plus\-Drude \(KD\) model with a PPT ionisation rate scaled to the TDSE's final electron density\. **Materials in structured entries:** None recorded. **Dataset quantities:** None recorded. **Contents:** 0 datasets; 0 formulas. Curation notes -------------- No datasets\: the only species is atomic hydrogen, which is not curated, and the results are shown in figures only \(the nonlinear polarizability Delta alpha\(I0\) = alpha\(I0\) \- alpha\(0\), Eqs\. 3\-6, against peak intensity\)\. Conventions\: p\(t\) = \, alpha\(w0\) = p\(w0\)/E\(w0\) \(Eqs\. 3\-4\), P = N p; the KD model is P\_NL,KD = eps0 \[n2 I\(t\) \- rho\(t\)/rho\_c\] E\(t\) \(Eq\. 7\), with n2 'the intensity\-independent nonlinear index \.\.\. extracted from TDSE calculations at weak intensity' \(no value printed\)\. Higher\-order Kerr claim \(notes only\)\: the TDSE nonlinear polarizability of hydrogen rises linearly with intensity, saturates and changes sign near 30 TW/cm^2, beyond the KD model, the excess following the fourth power of the intensity after the 10\-photon channel closure at about 32 TW/cm^2; the authors identify this 'quasi\-instantaneous' negative contribution with the empirical higher\-order Kerr effect of Loriot et al\. \(p\. 3\-4\), and quote channel\-closure intensities of 21\.5 and 48 TW/cm^2 \(Ar\), 32 and 57 TW/cm^2 \(O2\), 25 and 51 TW/cm^2 \(N2\) \(p\. 4, no source given\)\. They also note that the saturation appears only within the pump bandwidth, consistent with the two\-colour measurements \(Wahlstrand et al\.\) that see no saturation, and that 'plasma grating effects could have a partial contribution' \(p\. 4\)\. Status\: a theoretical support for a transient negative contribution tied to ionisation in a single atom, not a set of Kerr coefficients; the measured bound\-electron response of real gases stays linear in intensity up to ionisation \(Wahlstrand et al\. 2012, 2018\)\. Nothing to take\. **Recorded bibliographic identity status:** VALIDATED. This concerns identification of the source; it does not establish the scientific correctness of its contents. Datasets -------- No datasets are recorded. 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.