Carbon monoxide triplet Rydberg series in the f complex region

Using a multistep state-selective excitation scheme. fluorescence-dip spect ra of carbon monoxide have been recorded in the energy region between 106 1 00 and 112 200 cm(-1). Prominent groups of bands were tentatively identifie d as transitions into the 6f...10f (upsilon = 0) and 9p sigma...11p sigma ( upsilon = 0) triplet Rydberg series. For the f complex states, molecular co nstants have been calculated. The triplet f levels show an unusually large rotational constant and are located at higher energies than their singlet c ounterparts. (C) 2001 Academic Press.