Dr. Darrin J. Bellert

Associate Professor
High Res Photo

Associate Professor


University of Florida

Postdoctoral Associate
University of Utah

Wright State University, Ohio

Physical Chemistry

The localization of an electron in a normally unoccupied molecular orbital will often create a radical anion in an unstable, transient electronic state. Such states have been implicated in mutagenesis, DNA repair mechanisms, and etchants within the semiconductor industry (to name a few). Despite these biological and industrial associations, the difficulty in creating and sustaining such short-lived species has precluded them from routine study.

We plan to overcome such adversities and study these challenging species via gas phase photodissociation laser spectroscopy. Neutral molecules will be seeded into a pulsed, supersonic jet source and expanded through a plume of low energy electrons (formed via the photoelectric effect), thus creating anions. Anions possessing a positive electron affinity will be extracted via an orthogonal accelerator and separated based on the charge-to-mass ratio in a custom TOFMS. The mass isolated anion packet will intersect a laser beam resulting in the resonant absorption of radiation and the electronic promotion into molecular orbitals rich in anti-bonding character. Resonant transitions will be detected by monitoring either the photo-ejected electron or, preferably, the dissociate daughter fragments (detection of fragments guarantee a maximal transition limewidth in accordance with the uncertainty principle, dEdt ≥ ћ; a bond cannot rupture any faster than it can vibrate).

Anion photodissociation spectroscopy, as detailed here, is conceptually the tandem combination of anion photoelectron spectroscopy and dissociative electron capture. This unique experiment will resolve transient anion states into vibronic progressions, explore the electronic landscape of simple molecules, and probe bond rupture dynamics resulting from the localization of electrons into anti-bonding MO's.