Spectroscopy and intensity measurements of the 3 nu(1)+3 nu(3) tetrad of (CO2)-C-12 and (CO2)-C-13

Three of the four components of the 3 nu (1) + 3 nu (3) tetrad of (CO2)-C-1 2-O-16 and (CO2)-C-13-O-16, labeled 30031, 30032, and 30033 in HITRAN notat ion, have been observed by intracavity laser absorption spectroscopy in the 10 450- to 11 000-cm(-1) region. The rotational analysis has yielded the r ovibrational parameters of the vibrational states. The experimental values are found to be in very good agreement with the rovibrational energies rece ntly predicted from variational calculations and reduced effective Hamilton ians. The absolute band intensity of these extremely weak transitions have been measured. The study of the relative intensities within the 3 nu (1) 3 nu (3) tetrad suggests that part of the oscillator strength is carried by the (22(0)3) state. (C) 2001 Academic Press.