Infrared-microwave double resonance in CF 3I; Microwave spectroscopy in emission and absorption

Abstract

From the double resonance effects observed on the microwave spectrum of CF 3I it has been shown that the R(16) CO 2 laser line of the 9.4 μm band is coincident with the R(7), K = 2, F = 19 2 → 21 2 transition of the CF 3, symmetric stretch ( ν 1 band) of CF 3I. Using this laser line, 50 double resonance signals all with K = 2 were observed ranging from J = 4 → 5 to J = 12 → 13 transition. The fact that double resonance effects were observable over such a large range of J was explained as being caused by very strong Δ J = ± 1, Δ K = 0 collisional transitions. Extremely large pumping effects were produced using 6 W of laser radiation, which caused relative changes in intensity ( ΔI I ) in ground state lines of up to 25. The population transfer into the excited state was so large that many excited state lines, which had previously been undetectable, produced signals up to 30 times more intense than the corresponding undisturbed ground state lines (i.e., values of ΔI I of ∼6000 were achieved). Population inversions were produced by the laser pump in many of the K = 2 microwave transitions, not only in those with levels directly pumped by the laser but also in some connected only by collisional transitions. The results was that many of the signals were observed as stimulated emissions rather than absorptions. The rotational constant and quadrupole coupling constants of CF 3I in the v 1 excited state are calculated and an estimation of the center of the ν 1 band is made. The absolute population shifts produced by the laser pump are estimated and the rate constants of the collisional transitions are discussed.