The propargyl radical, the most stable isomer of C<sub>3</sub>H<sub>3</sub>, is very important in combustion reactions, and a number of spectroscopic and dynamics studies have been performed over the years to study its reactivity. However, theoretical calculations have never been able to find a strong absorption around 240nm as seen in experiments. In this study, we calculated the electronic energy levels of the propargyl radical using the highly accurate multireference configuration interaction singles and doubles method with triples and quadruples treated perturbatively (denoted as MRCISD(TQ)). Calculations indicate that this absorption cannot be solely attributed to a simple Franck–Condon-allowed electronic state transition. It also suggests that MRCISD calculations can capture the main electronic energy contribution almost as well as MRCISD(TQ). The roles of vibrational and rotational nonadiabatic effects are currently under investigation.

Ultraviolet absorption of the propargyl radical around 240 nm

251st National Meeting (2016)

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