richter_2013 ============ M\. Richter, S\. Patchkovskii, F\. Morales, O\. Smirnova and M\. Ivanov, New J\. Phys\. 15, 083012 \(2013\) `Source record `__ · :doc:`Catalogue ` · :doc:`Review register ` DOI: `10\.1088/1367\-2630/15/8/083012 `__ **Source kind:** theory **Recorded technique:** Analytical \(dressed\-state, Floquet\) model of the Kerr response of an atom in a strong infrared field, and numerical TDSE for a 1D soft\-core hydrogenic model and the 3D hydrogen atom \(0\.5\-1\.8 um, bell\-shaped 4\-0\-4 and flat\-top 4\-40\-4 cycle pulses\) with varied simulation\-box sizes to isolate the Kramers\-Henneberger \(KH\) states\. **Materials in structured entries:** None recorded. **Dataset quantities:** None recorded. **Contents:** 0 datasets; 0 formulas. Curation notes -------------- No datasets\: the systems are a 1D model atom and atomic hydrogen \(not curated species\), and the results are figures of Re Delta alpha\_w\(F\) = d\_w\(F\)/F0 \- lim d\_w/F0 \(the nonlinear part of the polarizability at the driving frequency\) against intensity\. Higher\-order Kerr claim \(notes only\)\: the saturation and reversal of the Kerr response is caused partly by ionisation and partly by population of, and restructuring into, the laser\-dressed Kramers\-Henneberger \('bound states of a free electron'\) states; with the KH states absorbed by a small box the linear Kerr effect persists until ionisation, as in Kolesik's short\-range\-potential analysis \(p\. 8\)\. In 3D hydrogen the response saturates near 4\.3e13 W/cm^2 and reverses near 5\.6e13 W/cm^2 \(0\.9 um, short pulse\); for bell\-shaped pulses 'the saturation of the Kerr response happens just before ionization sets in\. The higher\-order Kerr effect appears to be real, but it is important only in a very narrow intensity window\. As soon as ionization occurs, the free electrons start to dominate' \(Conclusions\)\. Status\: a mechanism study for hydrogen; it supports neither Loriot's coefficients nor a perturbative n4 \.\.\. n10 series for real gases, and is consistent with the measured linear response up to ionisation \(Wahlstrand et al\. 2012, its ref\. 39\)\. **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.