Many gas-phase hydrocarbon free radical species produced during thermal irradiation of polyethylene polymers have been studied in detail by means of Li+ ion attachment mass spectrometry (Li(+)IAMS). Spectra of the thermal decomposition products, detected by means of the Li+ ion attachment technique, clearly show that radicals, such as CnH2n+1 (n = 5-12) and CnH(2n+1) (n = 5-11), were the predominant species produced. Many of these species have been identified for the first time by mass spectrometry. Our results present direct evidence that free radicals are formed in the pyrolysis environment and are detectable with mass spectrometric techniques. (C) 2011 Elsevier B.V. All rights reserved.