The vibrationless (A)over-tilde←(X)over-tilde transition of the jet-cooled deuterated methyl peroxy radical CD3O2 by cavity ringdown spectroscopy

The nearly rotationally resolved spectrum of the (A) over tilde (2)A(')<-(X) over tilde (2)A() 0(0)(0) transition of perdeutero methyl peroxy near 1.35 mu m has been studied via pulsed cavity ringdown spectroscopy. Albeit, this is a weak transition, it is possible to observe the spectrum under jet-cooled conditions (approximate to 15 K) by combining a source of narrow-bandwidth radiation (approximate to 250 MHz) with a supersonic slit-jet expansion incorporating an electric discharge. The near infrared radiation was obtained by using stimulated Raman scattering and a pulsed, nearly Fourier-transform-limited Ti:sapphire amplifier seeded by a scanable cw Ti:sapphire ring laser. The experimental spectrum has been fitted using a model Hamiltonian that includes the rigid body rotation of an asymmetric top and the spin-rotation interaction. An excellent quality fit was obtained resulting in the determination of 15 molecular parameters characterizing the (A) over tilde and (X) over tilde states. Other results reported for CD3O2 include an estimate of the radical concentration and the vibronic transition dipole from the observed absorption intensities. Details about the spectral linewidths are also discussed. (c) 2007 American Institute of Physics.