L-shell X-ray production cross sections in metal oxide thin films due to 12C, 16O and 28Si ion beams at MeV SIMS energies

Successful co-implementation of different heavy ion beam nuclear analytical techniques such as heavy ion PIXE, ERDA, MeV SIMS and RBS hinges on the availability of accurate databases of fundamental ion beam-matter interaction parameters. We report on measurements carried out to determine L-shell X-ray production cross sections in ¹⁰¹Ru and ¹⁸¹Ta due to ¹²C, ¹⁶O and ²⁸Si projectile ions in the 0.2 MeV/u-1.0 MeV/u energy range. Experimental data is compared to calculations by one of the most widely implemented X-ray ionisation theories in PIXE analyses - the ECPSSR theory in its modified United Atom (UA) version. Results show fairly good agreement between experiment and theory for the ¹⁸¹Ta target atoms, with the level of agreement improving as the Z_ion/Z_target ratio decreases and as beam energy increases. For ¹⁰¹Ru target atoms theoretical predictions tend to underestimate experimental data and the discrepancies increase with projectile mass and decreasing energy. The contribution of projectile electron capture (EC) to the measured X-ray production cross sections is also considered in the data analysis and discussion.