{'fraction_non_alphanumeric': 0.012919896640826873, 'fraction_numerical': 0.015503875968992248, 'mean_word_length': 5.007751937984496, '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}}
Ultracold Surface Collisions : Sticking Probability of Atomic Hydrogen on Superfluid 4 He by

The sticking probability of atomic hydrogen on superfluid 4He has been measured for atom temperatures between 300 yuK and 4 mK. Data are presented for a superfluid 4He film at 85 mK on a sintered silver substrate with film thickness varied from 0.5 nm to a bulk puddle. The results of the sticking probability measurements for bulk 4He provide the first experimental evidence for universal quantum reflection and are in good agreement with recent theories. The observed film thickness dependence of the sticking probability clearly demonstrates the influence of the van der Waals-Casimir force due to the substrate. Thesis Supervisor: Thomas J. Greytak Title: Professor of Physics