Infrared Perpendicular Bands of Cyclopropane in the 3.5 Micron Region
The C-H stretching region of the infrared absorption spectrum of C(,3)H(,6) between 2898 and 3157 cm('-1) was recorded at Doppler-limited resolution ((TURN)0.0057 cm(' -1)) using a difference-frequency laser spectrometer system. A portion of the spectrum was deconvolved to (TURN) 1/2 of the Doppler width ((TURN)0.0027 cm('-1)). The main bands in this region are (nu)(,6) (A(,2)(''')) and (nu)(,8) (E') accompanied by a number of combination bands enhanced by resonance with the fundamentals. The upper state of the perpendicular band (nu)(,8) occurring near 3022 cm('-1) is in Fermi resonance with (nu)(,2) + (nu)(,9), which appears fairly strongly near 2934 cm('-1), with (nu)(,7) + (nu)(,9) + (nu)(,14) located only 9 cm('-1) above (nu)(,8), and with (nu)(,2) = 2(nu)(,14) near 3014 cm('-1). Additional weaker perturbations of the (nu)(,8) state are present. The (nu)(,2) + (nu)(,9) combination is in turn very severely perturbed by several other states. A Hamiltonian matrix, including (nu)(,8), (nu)(,2) + (nu)(,9), (nu)(,7) + (nu)(,9) + (nu)(,14), (nu)(,2) + 2(nu)(,14), and several other perturbing states, has been used for the treatment of the observed energy levels with the aid of a computer program for combined Hamiltonian analysis of rovibrational spectra that result from several interacting states. The resulting "deperturbed" spectroscopic constants and the interaction constants are reported. Highly accurate values for the ground state constants B(,0), D(,J), and D(,JK) a have also been obtained in the analysis, via a fit to combination differences from these data and from high-resolution FTIR spectra of the (nu)(,10) and (nu)(,11) bands. The fairly well-determined value of C(zeta)(,eff) for the (nu)(,2) + 2(nu)(,14) combination allowed C(zeta)(,14) to be determined with much improved accuracy, and (xi)-sum considerations then yielded an improved estimate of C(zeta)(,13) as well.
- Pub Date:
- Physics: Molecular