{'fraction_non_alphanumeric': 0.020671834625323, 'fraction_numerical': 0.00904392764857881, 'mean_word_length': 5.6239316239316235, '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}}
Electron relaxation in metals and high-Tc superconductors on the 10-fs timescale

We perform two-colour pump probe experiments on metals and superconductors using synchronized 10-fs pulses generated by optical parametric amplifiers, tunable from the visible to the near-infrared, mapping with unprecedented detail the energy equilibration dynamics of the free electron gas. In gold films we observe dramatic changes of the differential reflectivity spectrum on the 100-fs timescale, corresponding to the establishment of the thermal electron distribution, with dynamics dictated by excess energy. In high-Tc cuprate superconductors we observe fast electron relaxation, attributed to a strong electron-phonon coupling which may play a role in the superconductivity mechanism.