Infrared-microwave double-resonance and two-photon experiments on propynal with CO 2 lasers

Abstract

A large number of intense infrared-microwave double-resonance signals have been observed with propynal using several CO 2 laser lines in the region of 940 cm −1. From analysis of the effects observed with the P(22) line of the normal CO 2 laser and the R(34), 13CO 2 laser line, the rotational constants of three highly excited vibrational states were determined. Two infrared transitions in coincidence with the P(22) line were identified as the close doublet J′ ← J″ = 2 20 ← 3 21; 2 21 ← 3 22 of the ( v 11 = 1; v 6 = 1) ← 0 combination band and the transition J′ ← J″ = 2 12 ← 2 11 of the hot-band ( v 8 = 1; v 6 = 1) ← ( v 8 = 1). In the case of the K −1 = 2 doublet a large number of collisionally induced signals were observed. The transition in coincidence with the R(34), 13CO 2 laser line was identified as J′ ← J″ = 4 14 ← 4 23 transition of the hot-band ( v 6 = 1; v 9 = 1) ← ( v 9 = 1). Triple-resonance experiments were used to confirm the assignment and measure a further transition in the upper state of this band. Two-photon inverse Lamb dips were observed with both laser lines and the frequencies of three infrared transitions were determined with an absolute accuracy of ± 3 MHz. Preliminary constants for 14 other vibrational states with energy up to 900 cm −1 are presented.