Essential Elements

Department of Chemistry and Biochemistry
Physical Chemistry Seminar Series

Professor John Hardwick, University of Oregon
Monday, June 3, 2024—2:00pm
Tykeson 140
Hosted by: Jeff Cina

Electron detachment in the infrared: the spectrum and structure of HNO– in the infrared

Over the past few decades, the importance of ions in both common and exotic chemical processes has become obvious. The chemistry of flames, atmospheres, and astronomical objects all involve ion-molecule and ion-ion reactions, some of which are critical in understanding the complex reaction kinetics in those systems. In many such environments, the best way of observing the abundance of molecular ions is high resolution spectroscopy.

The spectra of positive ions are often observed in emission or absorption in laboratory discharges, since positive ions can survive in high temperature environments. Negative ions, on the other hand, often will detach an electron under moderate thermal conditions, since molecular electron affinities are rarely above 1 or 2 electron volts. Rotationally resolved spectra of molecular anions are, as a result, relatively rare.

The HNO– ion is known to have an electron detachment energy of 0.338 eV (about 2776 cm–1). We have recorded the rotationally resolved vibrational spectra of H14NO– and H15NO– near 3000 cm–1. The rotational analysis indicates that the origin of the vibrational band is only about 20 cm–1 above this limit. The analysis requires a determination of the geometry that can be compared with previous experimental and computational studies.