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

We report the rotational analyses of six bands of the B̃−X̃ electronic transition of jet-cooled 1-butoxy radical
and 11 bands of the corresponding transition in 1-pentoxy radical. From these spectra, we have obtained
experimental values for the rotational and spin-rotational constants in the X̃ state and the rotational constants,
vibrational frequencies, and band origins in the B̃ state. By comparing the rotational and spin-rotational constants
from these analyses with corresponding values from quantum chemistry computations, we assign the observed
spectra to the electronic origins and excited vibrational levels of the B̃ state of three distinct conformers of
1-butoxy and five distinct conformers of 1-pentoxy. These assigned bands can be used as unambiguous
diagnostics of the radical species, its structural isomer, and its conformation. These data can be used to identify,
and to some extent rationalize, distinctively different conformer stabilities in the X̃ and B̃ states and conformer-dependent dynamical behavior.