Knowledge Bank

Pulsed laser vaporization of thin carbon films has been used to produce gas phase carbon species under well controlled experimental conditions. Using this technique, we have observed chemiluminescence from the oxidation of these species by molecular oxygen. The carbon beam is shown by mass spectrometry to contain the following species (in order of their relative abundance): $C3>C>C2>>C4\simeq C5.$ Spectroscopic analysis of the chemiluminescence produced in the reaction of these gas phase species with molecular oxygen is used to identify the reaction product as chemiexcited diatomic carbon, $C2\ast$. The pressure dependence of the chemiluminescence and spectroscopic analysis are consistent with the following reaction $C3+02\to C2\mathrm{<mrow\; data-mjx-texclass="ORD">\ast </mrow>}+CO2.$ Preliminary experiments under single collision molecular beam conditions confirm that this single reaction step does occur.