Investigation of gas separation technique based on selective rotational excitation of different species by a laser

In this work, a gas separation approach based on the selective rotational excitation of different species is investigated. The presented method is particularly suitable for separating gases of similar or equal masses, such as isotopes and isomers. The selective rotational excitation is achieved by a targeted application of multiple non-resonant ultrashort laser pulses. Upon collision with a solid surface, a part of the excited rotational energy gets transferred into translational energy. By creating a discernible difference in average thermal velocities between the species of similar masses, an increased diffusivity of the excited species can be utilized for its successful separation. In order to test the validity of the novel separation technique, a comprehensive computational framework was developed. The energy transfer in gas-surface collisions was analyzed in great detail using a state-of-the-art molecular dynamics code, and the obtained data offered invaluable insight into the nature of scattering dynamics. Furthermore, a novel data-driven approach to gas-surface interaction modeling based on the recently introduced distribution element tree method was proposed. Relevant numerical and experimental data on the selective rotational excitation were gathered, and they served as an input for the performed numerical simulations. Using the developed computational framework, the validity of the proposed separation scheme was tested on a mixture of two species with identical mass. The obtained data offer numerical evidence supporting the proposed separation concept.