A diode-laser-based spectrometer for in-situ measurements of volcanic gases

We report the first results of the field operation of a novel, portable diode-laser spectrometer for gas-concentration measurements in volcanic areas. Remote detection of direct absorption line shapes was possible thanks to a telecom single-mode optical fiber that delivered radiation from a room-temperature distributed-feedback diode laser, emitting at 1.997 mum, to an open-path multiple-reflection cell, placed on gas effluxes. The system was deployed on two different active volcanoes in Italy, where simultaneous and continuous monitoring of CO2 and H2O concentrations has been demonstrated.