Upper stark state collisional relaxation cross sections for single rotational states of CH3F

A radiofrequency electric resonance cell has been used to modulate individu al rotational states present in a state-selected molecular beam of symmetri c top molecules prepared for use in a beam attenuation experiment. Tagging states in this way allows cross sections for collisionally induced Delta M transitions to be measured for single rotational states. A hexapole transmi ssion curve attenuation method reported earlier suffered from poor rotation al state resolution and the measurement of cross sections was very time con suming in comparison to the method reported here. Cross sections measured u sing the two different methods show remarkably good agreement.