Rotationally resolved B̃–X̃ electronic spectra of both conformers of the 1-propoxy radical

Abstract

Five bands of the B̃–X̃ laser induced fluorescence spectrum of jet-cooled 1-propoxy radical have been recorded with a spectral resolution of ≈200 MHz. The resolved rotational and fine structure of these bands has been assigned and analyzed providing rotational constants for both the X̃ and B̃ states as well as components of the electron spin-rotation tensor in the X̃ state. By comparison of these constants with ones obtained from quantum chemistry calculations, two bands have been assigned to the gauche (G) conformer of 1-propoxy and 3 bands to the trans (T) conformer. The spectrum of each conformer abruptly terminates after the excitation of a single C–O stretch.

Rotationally Resolved Electronic Spectra of the B̃−X̃ Transition in Multiple Conformers of 1-Butoxy and 1-Pentoxy Radicals

“…We reported a similar observation in the case of 1-propoxy. 17 In that work, the difference in rotational stucture between different groups of vibronic bands was confirmed to be due to the two different conformers of the 1-propoxy radical by means of detailed rotational analysis. It is likely that the three sets of bands of 1-butoxy shown in Fig.…”

“…This band is analogous, in terms of rotational structure, to band B of 1-propoxy whose carrier was likewise shown to be a C s trans conformer. 17 In that work we demonstrated that all six rotational constants can be determined in principle from the spectra and a similar argument holds for 1-butoxy. As suggested by Table 1, all conformers of 1-butoxy are near prolate symmetric tops.…”

“…The general method for analytically determining the number of conformers of the primary alkoxy radicals has already been described in our 1-propoxy paper, 17 and can be extended to 1-butoxy and 1-pentoxy. In 1-butoxy, there are two pairs of three-bond sets, i.e., C 2 -…”

“…Likewise, the calculation of the eigenvalues of H and the rotational intensities of transitions between theB andX states have been previously discussed. 17 However it is important to bear in mind the number of spectroscopic parameters that need to be fit to the high-resolution spectra. The six rotational constants viz., A , B , and C in the ground state, and A , B , and C in the excitedB state need to be fit to the spectra.…”

“…In a recent paper, we reported the analyses of the rotational structure 17 in the high resolution spectra of a number of bands of 1-propoxy. Using the rotatonal analysis to "bar code" the observed bands, we were able to assign them to two different conformers of 1-propoxy.…”