{'fraction_non_alphanumeric': 0.04395604395604396, 'fraction_numerical': 0.03076923076923077, 'mean_word_length': 4.7, '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}}
Sub-ppm multi gas sensing based on photoacoustic spectroscopy using DFB laser diodes

Sensitive photoacoustic detection of methane (CH4), hydrogen chloride (HCI) and water vapour (H2O) in the near-infrared range using semiconductor DFB lasers is reported. A detection limit of 0.17 ppm of CH4, 0.2 ppm of HCI and 0.024 ppm of H2O (signal-to-noise ratio = 3) is reached using a properly designed photoacoustic cell operating in its first longitudinal mode.