Electronic spectroscopy of the alkoxy radicals

Alkoxy radicals were produced in a supersonic free-jet expansion and probed via laser induced fluorescence spectroscopy. Over 20 alkoxy radicals (C_nH_{2n +1}O) containing from 3–12 carbon atoms were investigated at moderate (0.1 cm−1) resolution by probing the B˜ − X˜ electronic transition to obtain vibrationally resolved spectra. The interpretation of these spectra in terms of serving as a diagnostic for detection and excited state vibrations and/or different conformations is discussed.; The diagnostics for the alkoxy radicals was further extended by studies aimed at obtaining their molecular structure. A few bands in the vibrationally resolved spectra of the primary alkoxy radicals, 1-propoxy, 1-butoxy, and 1-pentoxy were studied under high (0.01 cm−1) resolution to resolve the rotational structure. A method for the detailed rotational analysis of these bands was developed which involved a comparison of the experimentally determined molecular constants with those obtained from quantum chemistry computations. The rotational constants of the ground and excited states as well as the spin-rotation constants in the ground state were obtained from these spectra. A rotational bar-coding technique was used to assign the vibronic bands based upon the principle that the rotational structure of a given vibronic band bar-codes for the species carrying the spectrum. The assigned bands can be used as unambiguous diagnostics of the radical species, its structural isomer, and its conformation. The spectra also shed light on the dynamical properties of these radicals which will be important in ultimately understanding their photochemistry.