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A. C. BLAIR, T. HÄBER AND D. J. NESBITT, JILA, University of Colorado, Boulder, Colorado 80309-0440.
Velocity collimation in the slit supersonic discharge expansion results in a strong reduction in residual Doppler broadening, which makes possible resolution of spin-rotation fine structure in open shell radicals in the near infrared. By way of example, spin-rotation splittings in the vibrational ground and excited state have been observed in the ro-vibrational spectrum of the symmetric C-H-vibration (3055.07723(63) cm-1)of chloromethyl radical, for both K = 0 and 1 nuclear spin species. Rovibrational line shapes have been fitted to a spin-rotation Hamiltonian, including rotational-asymmetry splitting as well as hyperfine interactions. Spin-rotation coupling constants have been obtained for the vibrational excited state, with ground state values taken from microwave spectra.