Harmonic and Combination Bands in CO2

Abstract

The absorption bands of C${\mathrm{O}}_2$ at higher frequencies are important for the determination of anharmonic constants which characterize the potential function and for the location of upper levels in the vibration diagram of ${\nu }_1$ and ${\nu }_2$ in which resonance interaction appears. Only the odd harmonics are active. The band $3{\nu }_2$ at 5.0μ has been measured under high resolution and five zero branches identified, two originating in the normal state and three in the first excited state. The rotational structure of the strongest of these bands at 2078 ${\mathrm{cm}}^{-1\mathrm{}}$ is resolved. The band $3{\nu }_3$ at 1.43μ is a typical doublet. Combination bands near 2μ and 1.6μ are sufficiently resolved to show their contours and to permit for the first time a satisfactory determination of their positions.