Radiation Measurements 33 (2001) 193–202 www.elsevier.com/locate/radmeas Energy loss of heavy ions in gases: a comparative study P.K. Diwan a , Shyam Kumar b; ∗ , Gurinder Singh a , Lakhwant Singh a a Department of Physics, Guru Nanak Dev University, Amritsar 143 005, India b Department of Physics, Kurukshetra University, Kurukshetra 136 119, India Received 26 January 2000; accepted 16 August 2000 Abstract A comparative study of various energy loss formulations has been made using the calculated stopping power values and the corresponding experimental values for projectile ions with 8 6 Z 6 92 in 11 gaseous media: the ve monatomic rare gases (He to Xe), two diatomic gases (H2; N2) and four polyatomic compounds (CH4; C4H10; CO2 and CF4), in an energy range of ∼ 1–80 MeV=n. The merits and demerits of the adopted formulations are highlighted. It has been observed that the calculations based on SRIM-2000.38 recently developed by Ziegler provides best agreement with the experimental results for projectile ions with 8 6 Z 6 47 in all these absorbers except the H2 gas absorber. c  2001 Elsevier Science Ltd. All rights reserved. 1. Introduction Passage of heavy ions through matter and evaluation of associated energy loss have widespread and well-known applications in diverse disciplines (Ahlen, 1980). The stop- ping power for heavy ion in gases is of paramount impor- tance in nuclear reaction studies for the identication of reaction products using E −E telescope detectors (Kapoor and Ramamurthy, 1986). In the absence of analytical ex- pressions for the two basic input parameters for stopping power calculations, viz. the eective charge of the ion as a function of ion speed and the mean ionization potential of the target, the various energy loss formulations employ empirical= semi-empirical relations to determine these two parameters. The accuracy for estimating stopping power therefore depends on the quality of tness employed to workout these expressions. However, there is a continuous need to check the reliability of such formulations through comparison with the available experimental data. There are reports, which indicate that the experimental stopping power values for heavy ions in solids deviate signicantly from the often-used semi-empirical models (Sharma et al., 1995a, b, Kumar et al., 1997; Randhawa and Virk, 1996). * Corresponding author. Tel.: +91-1744-20410; fax: +91-1744-20277. E-mail address: kuru@doe.ernet.in (S. Kumar). Regarding the stopping power for heavy ions in gaseous media, only a few reports are available (Bimbot et al., 1989a, b, 1996; Herault et al., 1991; Pierce and Blann, 1968). In this paper, we have made an attempt to establish the validity of various stopping power formulations for gaseous absorbers through comparison with the available experimental data. Further, such a study is important in order to identify the variation in stopping power with the physical state of the absorber. Such variation is reported to be due to the higher ionic charge of the moving ion in solids relative to gaseous media (Bimbot et al., 1989b; Geissel et al., 1982, 1983). 2. Present work In the present work, a comparative study of dierent stop- ping power formulations, e.g. Benton and Henke (1969), Northclie and Schilling (1970), Mukherjee and Nayak (1979), Ziegler et al. (1985), Ziegler (1999) and Hubert et al. (1989), have been made using the respective calculated stopping power values vis-a-vis the available experimental stopping power values. The Northclie and Schilling tabu- lated stopping power values are available up to 12 MeV=n in a limited number of absorbers only. The computer code SRIM-2000.38 recently developed by Ziegler is used for stopping power calculations from Ziegler et al. (1985, 1999) formulation. The experimental stopping power data of Bimbot et al. (1989a, b, 1996), Herault et al. (1991) and 1350-4487/01/$ - see front matter c  2001 Elsevier Science Ltd. All rights reserved. PII:S1350-4487(00)00144-X