Ionization of CO molecule by electron impact S. Pal a , *, S. Prakash b , S. Kumar c a Department of Physics, Janta Vedic College, Ch C. S. University, Meerut, Baraut 250 611, India b Department of Physics, Department of Hons. and Evening Studies, Kurukshetra University, Kurukshetra 136 119, India c Department of Physics, Kurukshetra University, Kurukshetra 136 119, India Received 30 July 1996; revised 20 February 1997 Abstract The direct (CO + ), dissociative (C + ,O + ), double (CO + 2 ,C + 2 ) and triple (CO + 3 ) ionization cross-sections for CO molecule by electron impact have been calculated from threshold to 10 keV electron energies using a previously developed semi-empirical formula. The present results are compared with the available experimental data. For most of the ionic fragments, satisfactory agreement has been noticed.  1997 Elsevier Science B.V. Keywords: Electron impact; Cross-section; Dissociative ionization; Double ionization; Triple ionization; Carbon monoxide 1. Introduction Electron impact ionization of neutral particles is of importance in a number of fields, ranging from plasma physics to mass spectrometry. A large amount of experimental and theoretical work has been devoted in this century to the determination of the accurate electron impact ionization cross-sections. The theoretical and experimental situations concerning quantitative knowledge of absolute electron impact ioniza- tions is still unsatisfactory. In particular, the measurement and/or calculation of partial ioniza- tion cross-sections for the production of specific ions are not yet as accurate as required for many areas of applications. Because of the urgent need of these data (e.g. in radiotherapy, plasma chemistry, discharge modelling, quantitative mass spectrometry, etc.), there have been numerous recent experimental as well as theore- tical efforts using improved methods and con- cepts [1]. The present study is devoted to the parent molecule of carbon monoxide gas. Only a small amount of work has been carried out up to now on the electron impact ionization of CO mole- cule. Earlier experimental studies detailed partial ionization cross-sections of the electron impact production of various ions from CO—see for example Refs [2–10]. In this paper, we have produced quantitative and qualitative information on direct, dissocia- tive, double and triple ionization cross-sections of CO molecule by electron impact. The calcula- tions have been done using the method of Khare et al. [11,12]. Results reported in the present study include direct, dissociative, double and triple ionization cross-sections corresponding to 0168-1176/97/$17.00 Copyright  1997 Elsevier Science B.V. All rights reserved PII S0168-1176(97)00022-0 International Journal of Mass Spectrometry and Ion Processes 164 (1997) 13–17 * Corresponding author.