{'fraction_non_alphanumeric': 0.014450867052023121, 'fraction_numerical': 0.0009633911368015414, 'mean_word_length': 4.772222222222222, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Prospects of odd and even harmonic generation by an atom in a high-intensity laser field

A new approach for studying the spontaneous emission of an atomic system in the presence of a high-intensity laser field is used to study the process of harmonic generation. The analysis is based on consideration of quantum system interaction, with the quantized field modes being in the vacuum state, while the intense laser field is considered to be classically beyond perturbation theory. The numerical analysis of the emission from the single one-electron 1D atom irradiated by the femtosecond laser pulse of a Ti:Sa laser is discussed. It is demonstrated that not only odd, but also even harmonics can be emitted if the laser field is strong enough. The origin of the appearance of even harmonics is studied. The obtained results are compared with those found in the framework of the semiclassical approach that is widely used to study harmonic generation. It is found that the semiclassical approach is inapplicable in the strong-field limit.