Prof. Piergiorgio Casavecchia
Dipartimento di Chimica Universita’ degli Studi di Perugia
Via Elce di Sotto, 8 - 06123 PERUGIA, Italy

Phone: (+39) 075 585 5514
Fax: (+39) 075 585 5606


                                                    RESEARCH GROUP

                                                                                                                                                                                                                         PUBLICATIONS (1991-present)








Research Overview
Our main research activity is currently in the field of Chemical Reaction Dynamics. We aim at understanding “chemical reactivity” at the most fundamental level.
We use the Crossed Molecular Beam (CMB) scattering technique with rotating mass spectrometric detection and time-of-flight analysis to measure reactive differential cross sections for elementary chemical reactions of importance from a fundamental point of view and in areas of practical interest, such as atmospheric-, combustion- and astro-chemistry. From measurements of product angular and velocity distributions in the laboratory frame, we derive product angular and translational energy distributions in the center-of-mass system. From these we get information on (a) primary reaction products and branching ratios, (b) reaction micro-mechanisms (i.e., "direct" or via "long-lived complex"), (c) intermediate lifetimes and their unimolecular decay dynamics, (d) product energy partitioning (between translation and internal degrees of freedom), (e) details of the potential energy surface(s) for reaction.
    The main thrust of our work during the last few years has been that of investigating the reactive scattering of (a) oxygen atoms, (b) nitrogen atoms, (c) chlorine atoms, (d) carbon atoms, (e) hydroxyl radicals, (f) dicarbon radicals, and (g) cyano radicals with both inorganic and organic molecules. Reactive scattering of gas-phase atomic species from a liquid hydrocarbon surface in the thermal collision energy range was also investigated some time ago (in collaboration with Tim Minton, Montana State University). Recently, we have undertaken the investigation of the reaction dynamics of also sulfur atoms (often in synergic collaboration with the Rennes group (Ian Sims and Sébastien Le Picard) who perform very low temperature kinetics measurements). Key to our dynamics studies is the ability to generate intense, continuous supersonic beams of these transient species. Recently (2004), an improvement in the detection sensitivity of the CMB apparatus, based on the implementation, for the first time, of the "soft" electron-ionization method for product detection, has opened up the way to investigate the detailed dynamics of polyatomic multichannel reactions (as those of O-atoms with unsaturated hydrocarbons) and radical-radical reactions (as those of O-atoms with hydrocarbon radicals). At the same time, the CMB apparatus was equipped, for the first time in this kind of instruments, with the possibility of crossing the two reactant beams at angles both lower (45
degrees) and higher (135 degrees) than the usual 90 degrees. This permits to extend the range of collision energies (both on the low and high-energy side) that can be attained, and it is of importance for astrochemistry and combustion relevant reactions, respectively.

The experimental results for simple 3-atom and 4-atom prototype reactions are usually compared with those of dynamical calculations, both by quantum mechanical and quasiclassical trajectory methods, on the relevant potential energy surfaces within international collaborations with leading theoretical groups. Very recently, also for polyatomic nonadiabatic multichannel reactions (such as that of atomic oxygen with ethylene) it has become possible, within synergic international collaborations with the group of Joel M. Bowman at Emory University, to compare the experimental results with those of dynamical calculations (by the quasiclassical trajectory surface-hopping method) on full dimensional potential energy surfaces, accounting also for nonadiabatic effects (intersystem crossing).

Finally, a new laboratory has recently been set-up to characterize, by using Laser-Induced-Fluorescence (LIF) and Resonant-Enhanced-Multiphoton-Ionization (REMPI), the internal quantum state distributions of supersonic radical beams (such as C2 and CN) to be used in crossed molecular beam reaction dynamics studies.

The investigation of the dynamics of polyatomic multichannel reactions and radical-radical reactions is our major current effort.

Selected recent publications:

1.      The last mile of molecular reaction dynamics virtual experiments: the case of the OH(N=1-10)+CO(j=0-3) reaction”, Faraday Discuss. 157, xxx (2012) (Published on 18 April 2012 on | doi:10.1039/C2FD20046E)

2.      “Experimental and theoretical studies of the O(3P)+C2H4 reaction dynamics: Collision energy dependence of branching ratios and extent of intersystem crossing”, J. Chem. Phys. 137 (22), 22A532-1 - 22A532-22 (2012), []

3.      “Crossed molecular beam studies of bimolecular reactions of relevance in combustion”, Energy 43, 47-54 (2012), doi:10.1016/

4.      “Intersystem crossing and dynamics in O(3P)+C2H4 multichannel reaction: Experiment validates theory”, Proc. Natl. Acad. Sci. U.S.A., 109 (25) 9733-9738 (2012); (doi: 10.1073/pnas.1202672109)

5.      “Crossed Molecular Beam Dynamics Studies of the O(3P) + Allene Reaction: Primary Products, Branching ratios and Dominant Role of Intersystem Crossing”, J. Phys. Chem. Letters  3, 75-80 (2012)

6.       “Crossed-beam dynamics studies of the radical-radical combustion reaction O(3P) + CH3 (methyl)”, Phys. Chem. Chem. Phys., 13 (18), 8322 – 8330 (2011). (DOI:10.1039/C0CP01623C)

7.       “Low temperature kinetics, crossed beam dynamics and theoretical studies of the reaction S(1D) + CH4 and low temperature kinetics of S(1D) + C2H2”, Phys. Chem. Chem. Phys., 13 (18), 8485 - 8501 (2011) (DOI:10.1039/C0CP02813D)

8.       “Formation of nitriles and imines in the atmosphere of Titan: Combined crossed-beam and theoretical studies on the reaction dynamics of excited nitrogen atoms N(2D) with ethane”, Faraday Discuss. 147, 189-216 (2010) (DOI: 10.1039/C004748A)

9.       “Reactive scattering: reactions in three dimensions”, P. Casavecchia, K. Liu, and X. Yang, In: Tutorials in Molecular Reaction Dynamics, Mark Brouard & Claire Vallance, eds. (Royal Society of Chemistry Publishing, Cambridge, UK), Ch. VI (2010), pp. 167-213.

10.   “The dynamics of the C(1D)+H2 reaction: a comparison of crossed molecular beam experiments with quantum mechanical and quasiclassical trajectory calculations on the first two singlet (11A’ and 11A”) potential energy surfaces”, Mol. Phys. 108, 373-380 (2010) (DOI: 10.1080/00268970903476696)

11.   “Crossed-beam universal-detection reactive scattering of radical beams characterized by laser-induced-fluorescence: the case of C2 and CN”, Mol. Phys. 108, 1097-1113 (2010) (DOI: 10.1080/00268971003657110

12.   “Crossed-beam dynamics, low temperature kinetics and theoretical studies of the reaction S(1D) + C2H4”, J. Phys. Chem. A  113, 15328-15345 (2009) (DOI: 10.1021/jp906299v)

13.   “Crossed-beam and theoretical studies of the S(1D) + C2H2 reaction”, J. Phys. Chem. A 113, 4330-4339 (2009) (DOI: 10.1021/jp810989p)

14.   “Combined crossed molecular beam and theoretical studies of the N(2D)+CH4 reaction and implications for atmospheric models of Titan”, J. Phys. Chem. A 113, 11138-11152 (2009) (DOI: 10.1021/jp904302g).

15.    “Probing the dynamics of polyatomic multichannel elementary reactions by crossed molecular beam experiments with soft electron-ionization mass spectrometric detection”, Phys. Chem. Chem. Phys. 11, 46-65 (2009). (Perspective, Front Cover) (DOI: 10.1039/B814709D)

16.   “Beyond the Lennard-Jones model: A simple and accurate potential function probed by high-resolution scattering data useful for molecular dynamics simulations”, Phys. Chem. Chem. Phys. 10, 5489–5503 (2008) (Perspective, Front Cover) (DOI: 10.1039/b808524b)

17.   The extent of non-Born-Oppenheimer coupling in the reaction of Cl(2P) with para-H2”, Science 322, 573-576 (2008).

18.   “Unraveling the dynamics of the C(3P,1D) + C2H2 reactions by the crossed molecular beam scattering technique”, J. Phys. Chem. A 112, 1363-1379 (2008) (DOI: 10.1021/jp0776208)

19.   “Crossed molecular beam studies of radical-radical reactions: O(3P) + C3H5 (allyl)”, Phys. Chem. Chem. Phys. 9, 1307–1311 (2007) (DOI:10.1039/ B618971G)

20.   “Crossed molecular beam reactive scattering: From simple triatomic to multichannel polyatomic reactions”, Int. Rev. Phys. Chem. 25, 109-163 (2006).

21.   “Experimental and theoretical differential cross sections for the N(2D)+H2 reaction”, J. Phys. Chem. A 110, 817-829 (2006)

22.   “Dynamics of the O(3P)+C2H4 reaction: Identification of five primary product channels (vinoxy, acetyl, methyl, mthylene, and ketene) and branching ratios by the crossed molecular beam technique with soft electron ionization”, J. Phys. Chem. A 109 (16), 3527 (2005) (Letter, Front Cover)

23.   “The dynamics of the prototype abstraction reaction Cl(2P3/2,1/2) + H2: A comparison of crossed molecular beam experiments with exact quantum scattering calculations on coupled ab initio potential energy surfaces”, Phys. Chem. Chem. Phys. 6, 5007-5017 (2004)

24.   “Dynamics of the insertion reaction C(1D) + H2: A comparison of crossed molecular beam experiments with quasiclassical trajectory and quantum mechanical scattering calculations”, Phys. Chem. Chem. Phys. 6, 4957-4967 (2004)

25.   Soft electron impact ionization in crossed molecular beam reactive scattering: the dynamics of the O(3P) + C2H2 reaction”, J. Chem. Phys. 120, 4557-4560 (2004)

26.   “Crossed molecular beam reactive scattering: towards universal product detection by soft electron-impact ionization”, In "Modern Trends in Chemical Reaction Dynamics, Part II: Experiment and Theory”, Advanced Series in Physical Chemistry, Vol. 14, Ed. by Xueming Yang and Kopin Liu (World Scientific, Singapore, 2004), Ch. 7 (pp. 329-381).

27.   “Differential cross sections from quantum calculations on coupled ab initio potential energy surfaces and scattering experiments for Cl(2P) + H2 reactions”, Phys. Rev. Letters 91, 013201-1-013201-4 (2003)

Less recent:

1.       "Chemical reaction dynamics with molecular beams", Rep. Prog. Phys. 63, 355-414 (2000)

2.       "Cyanomethylene formation from the reaction of excited nitrogen atoms with acetylene: a crossed beam and ab initio study", J. Am. Chem. Soc. 122, 4443-4450 (2000)

3.       "Crossed beam studies of reaction dynamics", Annu. Rev. Phys. Chem. 50, 347-376 (1999)

4.       "Reactive scattering of oxygen and nitrogen atoms", Acc. Chem. Res. 32, 503-511 (1999)

5.       “Reactive scattering of ground state and electronically excited oxygen atoms on a liquid hydrocarbon surface", Faraday Discuss. 108, 387-399 (1997)

6.       "The dynamics of the reaction OH+D2-> HOD+D: Crossed beam experiments and quantum mechanical scattering calculations on ab initio potential energy surfaces", Chem. Phys. 207, 389-409 (1996)

7.       "Dynamics of the simplest chlorine atom reaction: An experimental and theoretical study", Science 273, 1519-1522 (1996)

8.       "Reactive scattering of atoms and radicals", J. Chem. Soc. Faraday Trans. (Faraday Research Article) 91, 575-596 (1995)

9.       “Crossed Beam Studies of Four-Atom Reactions: The Dynamics of OH + CO”, J. Chem. Phys. 98, 8341-8344 (1993)


1950 : Birth, Marsciano (Perugia), Italy
1974 : "Laurea" in Chemistry, University of Perugia (Italy).
1974-1977 : Research Fellow, Department of Chemistry, University of Perugia (Italy).
1977-1980 : Post-doctoral fellow with Professor Y.T. Lee, Department of Chemistry and Lawrence Berkeley Laboratory, University of California, Berkeley, CA (USA).
1980-1987 : Research Associate, Department of Chemistry, University of Perugia (Italy).
1987-2001 : Associate Professor of Physical Chemistry (Chemical Kinetics and Molecular Dynamics), University of Perugia (Italy).
2001- present : Full Professor of Physical Chemistry, University of Perugia (Italy).

1997: Professeur Invite, University of Paris-Sud, Orsay, France
2000: Miller Visiting Professor, University of California, Berkeley, USA
2002: Erskine Visiting Professor, University of Canterbury, Christchurch, New Zealand 

2007: Visiting Professor, Dalian Institute of Chemical Physics, CAS, Dalian, China


Member of the Editorial Board of PCCP (Physical Chemistry Chemical Physics)(2006-2011).
Member of the International Advisory Board of the "Journal of Physical Chemistry" (2006-2008).
Member of the International Advisory Board of "Chemical Physics" (2007-).
Member of the International Advisory Board of "Chemical Physics Letters" (2009-).

Member of the International Advisory Board of PCCP (Physical Chemistry Chemical Physics) (2012-).

Board Member of the Molecular Physics Section of the European Physical Society (EPS) (2004- ).

Scientific Secretary of the International Symposium on Molecular Beams (2002- ).
Fellow of the Royal Society of Chemistry (FRSC)

Member of ACS and APS


Chairman of the XVI International Conference on Molecular Energy Transfer - COMET XVI (Assisi, Italy, 20-25 June 1999).
Chairman of 26th International Symposium on Free Radicals (Assisi, Italy, 2-7 September 2001).
Chairman of XIV Symposium on Atomic and Surface Physics - SASP 2004 (La Thuile, 2004).

Chairman of Faraday Discussion 157 “Molecular Reaction Dynamics in Gases, Liquids and Interfaces” (Assisi, Italy, 25-27 June 2012).


- Team Leader in the European Training and Mobility of Researchers (TMR) Network (1997-2001) "ASTROPHYSICAL CHEMISTRY: Experiments, Calculations and Astrophysical Consequences of Reactions at Low Temperatures" (FP4)
Co-ordinator of the European Research Training Network (RTN) (2000-2004) "REACTION DYNAMICS: Experimental and Theoretical Studies on the Dynamics of Reactions of Atoms and Radicals of Fundamental and Practical Importance". (FP5)
Team Leader in the European Commission Marie Curie Research Training Network (2004-2008): “The Molecular Universe: An interdisciplinary programme on the physics and chemistry of molecules in space”. (FP6)

- Team Leader in the European Commission Research Infrastructure Action (2004-2008): "European Planetology Network (EUROPLANET)". (FP6)


- AWARDS: Polanyi Medal 2008.

                                                                                                                                                                   last update: Jan 2012