Rotational analysis of the electronic spectrum of the allyl radical

Abstract

The rotationally resolved

electronic spectra of the allyl radical C₃H₅ and its isotopic derivative C₃D₅ have been recorded in the gas phase by cavity ring down spectroscopy through a supersonic planar plasma. A rotational analysis yields accurate molecular constants for the first excited electronic state with T ₀₀ = 24 491.229 2(80) for C₃H₅. A C_{2 v} planar structure in the zero-point level is indicated. The obtained rotational constants were employed to determine the C–C bond length 1.48 Å and the CCC bond angle 123° in the ²B₁ electronic state. Two other bands observed are assigned to the excitation of the ν₇ (339 cm⁻¹) and ν₉ (101 cm⁻¹) vibrational modes in the upper electronic state.

Acknowledgement

This work has been supported by the Swiss National Science Foundation (project 200020-100019/1).