Time-domain measurements of pressure-induced frequency shifts in methyl chloride and ethylene oxide

Pressure-induced rotational frequency shifts at microwave frequencies have been measured in the time domain. The computerized technique involves using the Stark effect to move molecules into resonance with an incident microwave field. The heterodyned emission decay signals can then be fitted for the frequency and relaxation time. Measurements are reported for the three J = 0–1 hyperfine transitons of CH3 35Cl and three ethylene oxide transitions 211–202, 321–330, and 431–422.