Penning ionization of 2-bromothiophene and 3-bromothiophene by collision with He*(23S) metastable atoms is studied using two-dimensional (collision-energy and electron-energy-resolved) Penning ionization electron spectroscopy. Some satellite bands correlated with ionic states of π orbitals are observed in Penning ionization electron spectra. Collision energy dependence of partial ionization cross sections indicates that attractive interactions of the He* out-of-plane approach respective to the thiophenyl ring including bromine atom are much stronger than those of the in-plane approach. Substitution of the bromine atom holds the sequence of magnitude of attractive interaction for the out-of-plane approach π2 > π3 > ns which was previously observed for thiophene. Different substitution sites lead to the change of Penning ionization activity of the in-plane lone pair orbital of the bromine atom, which is interpreted as a result of intramolecular orbital interactions.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry