9776 | Phys. Chem. Chem. Phys., 2014, 16, 9776--9790 This journal is © the Owner Societies 2014 Cite this: Phys. Chem. Chem. Phys., 2014, 16, 9776 Directions of chemical change: experimental characterization of the stereodynamics of photodissociation and reactive processes† Toshio Kasai,* ab Dock-Chil Che, b Michio Okada, b Po-Yu Tsai, ac King-Chuen Lin, ac Federico Palazzetti d and Vincenzo Aquilanti* d This perspective article aims at accounting for the versatility of some current experimental investigations for exploring novel paths in chemical reactions. It updates a previous one [Phys. Chem. Chem. Phys., 2005, 5, 291] and is limited to work by the authors. The use of advanced molecular beam techniques together with a combination of modern tools for specific preparation, selection and detection permits us to discover new trends in reactivity in the gas phase as well as at interfaces. We specifically discuss new facets of stereodynamics, namely the effects of molecular orientation and alignment on reactive and photodissociation processes. Further topics involve roaming paths and triple fragmentation in photodissociation probed by imaging techniques, chirality effects in collisions and deviations from Arrhenius behavior in the temperature dependence of chemical reactions. I. Introduction 1. Motivation There is an ample consensus in Western science on dating the birth of chemistry at the end of the 18th century, when Lavoisier demonstrated that basic phenomena such as combustion and oxidation occur by the addition of a volatile gas to organic matter or metals. This gas, which generates oxides, was accordingly baptized oxygen. This was a revolutionary event: previously, among alchemists a Department of Chemistry, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan b Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan c Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 10617, Taiwan d Dipartimento di Chimica, Universita` di Perugia, via Elce di Sotto, 8 – 06123 Perugia, Italy † This paper is published as part of the PCCP 15th anniversary issue. Toshio Kasai Toshio Kasai received Dr. Sci. degree from the Graduate School of Science, Osaka University in 1979. He became a full professor of Osaka University in 1995. He is now a professor Emeritus of Osaka University and a visiting professor of National Taiwan University since 2010. His main interest has been focused on stereo-dynamical effects in chemical reactions using oriented molecular beams and lasers. His interests extend to cellular respiration, auto-catalytic reaction and cultural heritage chemistry. Dock-Chil Che Dock-Chil Che received a Ph. D. degree from the Department of Chemistry, Graduate School of Science, Osaka University in 1993. From 1992 to 1994, he was a Research Fellow supported by the Japanese Society for the Promotion of Science. From 1995 to 1996, he was a Postdoctoral Fellow at IAMS in Taiwan. From 2012, he is Associate Professor in the Department of Chemistry, Graduate School of Science, Osaka University. His scientific interests are the reaction dynamics of radicals with small molecules, and the spectroscopy of small molecules. Received 30th January 2014, Accepted 14th April 2014 DOI: 10.1039/c4cp00464g www.rsc.org/pccp PCCP PERSPECTIVE Published on 14 April 2014. Downloaded by University of Perugia on 09/05/2014 10:02:12. View Article Online View Journal | View Issue