High rate concentration measurement of molecular gas mixtures using a spatial detection technique

Abstract

Concentration measurement in molecular gas mixtures using a snapshot spatial imaging technique is reported. The approach consists of measuring the birefringence of the molecular sample when field-free alignment takes place, each molecular component producing a signal with an amplitude depending on the molecular density. The concentration measurement is obtained on a single-shot basis by probing the time-varying birefringence through femtosecond time-resolved optical polarigraphy (FTOP). The relevance of the method is assessed in air.

Probing ultrafast thermalization with field-free molecular alignment

“…Due to the thermal averaging, a change in the temperature and therefore in the initial state distribution affects both the amplitude and shape of cos 2 θ T (t). This dependence with respect to T is a feature that makes the concept of field-free alignment particularly useful for non-resonant space-resolved optical diagnostics [17,18].…”