{'fraction_non_alphanumeric': 0.01736745886654479, 'fraction_numerical': 0.007312614259597806, 'mean_word_length': 5.676829268292683, '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}}
Time-resolved photoelectron angular distributions and cross-section ratios of two-colour two-photon above threshold ionization of helium

Time-resolved anisotropy parameters and cross-section ratios of the positive and negative sidebands from two-colour two-photon above threshold ionization of helium atoms are measured using photoelectron velocity map imaging with the selected 19th high-order harmonic at 29.1 eV in an 810 nm perturbative dressing field. The intensities of both the sidebands and the single-photon ionization depletion follow a Gaussian correlation function where the photoelectron angular distributions and cross-section ratios of the sidebands do not change as a function of the temporal delay between the extreme ultraviolet and infrared pulses. The experimental results are compared with theoretical predictions using the soft-photon approximation, showing poor agreement, and analytical expressions are derived using second-order perturbation theory to determine the relative magnitudes of the resulting S and D partial waves of the above threshold ionization features.