PHYSICAL REVIEW A 87, 062701 (2013) Computation of electron-impact total and differential cross sections for allene (C 3 H 4 ) in the energy range 0.1–2000 eV Avani Barot, 1 Dhanoj Gupta, 2 Minaxi Vinodkumar, 1 and Bobby Antony 2,* 1 V P & R P T P Science College, Vallabh Vidyanagar 388 120, Gujarat, India 2 Department of Applied Physics, Indian School of Mines, Dhanbad 826004, Jharkhand, India (Received 4 April 2013; revised manuscript received 8 May 2013; published 3 June 2013) In the present article we report a comprehensive calculation of total and differential cross sections for electron impact on allene (C 3 H 4 ) molecule. The total cross sections are computed for a wide electron energy range from 0.1 eV to 2 keV. We have employed R-matrix code through QUANTEMOL-N software for ab initio calculations below 10 eV while intermediate- to high-energy calculations are performed using the spherical complex optical potential formalism. The two methods are found to be consistent at around 3 eV, merging smoothly. The results for both total and differential cross sections are in good agreement with previous results wherever available. We have also observed the presence of a shape resonance at 2.9 eV due to degenerate ( 2 B 1 , 2 B 2 ) states. The electronic excitation cross section for e-C 3 H 4 scattering is reported. DOI: 10.1103/PhysRevA.87.062701 PACS number(s): 34.80.Bm, 34.80.Ht I. INTRODUCTION The study of electron-impact total cross sections for hy- drocarbons plays an important role in varieties of applications such as radiation biochemistry, low-temperature processing plasmas, atmospheric and astrophysical phenomena, and modeling electron assisted processes in fuel combustion [1–3]. Since the early 1930s, there has been interest in studying the relationship between the structural properties of the target and the shape and magnitude of the total cross sections (TCS) [4–6]. Recently the study of electron-impact total cross sections with C 3 H 4 has geared up as it is the simplest hydrocarbon with isomeric effect. C 3 H 4 molecule has two stable isomeric molecular structures, viz., allene and propyne. Allene has one carbon atom with a double bond with each of its two adjacent carbon centers. The reactivity of allene with gaseous chlorine is more like that of alkynes than alkenes and hence is much more reactive than other alkenes [7]. The central carbon of allene forms two sigma bonds and two pi bonds (Fig. 1) with hydrogen atom. The central carbon is sp hybridized, and the two terminal carbons are sp 2 hybridized, with a linear geometry for the carbons of allene. Owing to the simple structure and stability, C 3 H 4 is a good candidate for investigation for both theoreticians as well as experimentalists. Besides, C 3 H 4 is a feed gas in plasma enhanced chemical vapor deposition for the growth of carbon nanotubes [8]. Hence, it is imperative to study the electron-impact scat- tering on allene to understand various processes in these environments. There are many studies concentrating on the isomeric effect of C 3 H 4 , its properties, and cross sections result- ing from interaction with electrons. Nakano et al. [9] measured the absolute differential cross section (DCS) for C 3 H 4 isomers (allene and propyne) from 1.5 to 100 eV. Szmytkowski and Kwitnewski [10] and Makochekanwa et al. [11] measured electron-impact TCS for C 3 H 4 isomers at low energies from 0.5 to 370 eV and from 0.8 to 600 eV, * bka.ism@gmail.com respectively. Lopes and Bettega [12] and Sanchez et al. [13] calculated elastic and differential cross sections at low energies using Schwinger multichannel method. From the literature survey it is very clear that there are more experimental investigations [9–11] as compared to theory [12,13]. It is also noteworthy to see that there are no theoretical or experimental results beyond 600 eV. Thus, the studies on e-C 3 H 4 scattering are fragmentary. Also, there is no comparison for electronic excitation cross sections in the literature to the best of our knowledge. Thus, in this article we present a comprehensive study that includes eigenphase diagram, electronic excitation cross sections, differential cross sections, and total and ioniza- tion cross sections over an extensive range of impact energies starting from very low energy of 0.1 to 2000 eV. Apart from the differential and total cross sections, we have also calculated total inelastic cross section comprised of total ionization and sum total of electronic excitations cross sections. Total ionization cross sections are then derived from Q inel using the complex spherical potential-ionization contribution (CSP-ic) method [14]. These Q ion are compared with the values reported by Kim and Irikura [15] using the binary-encounter-Bethe (BEB) method along with present computed BEB data through QUANTEMOL-N. The central idea behind the present study is to investigate all the phenomena that occur in an electron-impact scattering over a wide energy range from 0.1 to 2000 eV. At low electron- impact energies (<10 eV) short-lived anions (resonances) may be formed which may then subsequently decay to produce neutral and anionic fragments. Hence, the prediction of low- energy resonance formation, which is strongly linked with the forces acting on the electrons during the scattering process and therefore the structural properties of the target, can be of utmost importance in understanding the local chemistry. However, intermediate- to high-energy electron scattering cross sections are required in other fields such as astrophysics, atmospheric physics, and radiation physics, where high-energy radiations such as x rays, cosmic rays, etc., are present and interact with gases. These high-energy interactions can produce an avalanche of secondary electrons which then provide the low- energy electrons for further chemical reactions. Consequently, 062701-1 1050-2947/2013/87(6)/062701(9) ©2013 American Physical Society