Observation of Dgr;k=3nselection rule in collisionallyhyphen;induced transitions in methyl flouride

摘要

By varying the phase of the lockhyphen;in amplifier that processes the probe signal in an infraredndash;infrared doublehyphen;resonance spectrometer, the fourhyphen;level double resonances that result from collisionallyhyphen;induced rotational energy transfer in13CH3F are clearly distinguished from those that result from a vibrational energy swapping mechanism (Vndash;Venergy transfer). The spectrometer operates with a fixed frequency moderate power (sim;1 W) pumping source and a tunable low power (sim;20 mgr;W) probe source. At one choice of phase the absorption that results from collisionallyhyphen;induced rotational transitions are shown to have one sign in the spectrum and to obey the selection rule Dgr;k=3n(na positive or negative integer) whereas the peaks from all other collisionallyhyphen;induced transitions (Dgr;kne;3n) have the opposite sign. The sample spectrum is forJ=22, which shows that the Dgr;k=3nselection rule persists for manyJstates away from the originallyhyphen;pumped level (J=5).