A. W. Castleman, Jr.

A. W. Castleman Jr.

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  • Professor Emeritus
309 Chemistry Building
University Park, PA 16802
(814) 865-7242


  1. B.Ch.E., Rensselaer Polytechnic Institute, 1957
  2. M.S., Polytechnic Institute of New York. 1963
  3. Ph.D., Polytechnic Institute of New York, 1969

Honors and Awards:

  1. 2011-2014 Re-elected Liaison of Section 14 of the National Academy of Sciences to the National Research Council
  2. 2010-2013 Member Chemical Sciences Round Table NRC/NAS
  3. 2010 Irving Langmuir Award in Chemical Physics – American Chemical Society Award
  4. 2010 US Senior Scientist von Humboldt Award
  5. 2008-2011 Elected Liaison of Section 14 of the National Academy of Sciences to the National Research Council
  6. 2008 Royal Society of Chemistry (Fellow)
  7. 2007 Thomas W. Phelan Fellows Award (Rensselaer Polytechnic Institute Alumni Award)
  8. 2006-2008 Elected Vice Chair/Chair; Chemical Physics Division of the American Physical Society
  9. 2006 US Senior Scientist von Humboldt Award
  10. 2005-2007 Elected Chair, Gordon Conference on Clusters, Nanocrystals, and Nanostructures
  11. 2005-2007 Adviser/Foreign Councilor to the Director General of the Institute for Molecular Sciences (premier research institute, Okazaki, Japan)
  12. 2005 Conference Organizer and Chair - Femtochemistry VII , Washington DC
  13. 2000 Award of the Bunsen Gesellschaft (Chemical Society) – Akademie der Wissenschaften Zu Goettingeen Wilhelm-Jost Memorial Lectureship 2000 (at the 7 universities of Jost’s career)
  14. 2000 Invited Lecturer Nobel Symposium Physics and Chemistry of Clusters
  15. 2001-2006 Member and Chair of the Board of Chemical Sciences and Technology, National Research Council
  16. 1999 Appointed Eberly Distinguished Chair in Science
  17. 1998 Elected Member of the National Academy of Sciences
  18. 1998 Elected Fellow of the American Academy of Arts and Sciences
  19. 1998 Elected Fellow of the New York Academy of Sciences
  20. 1998 US Senior Scientist Humboldt Award
  21. 1997 Awardee of Senior Scientist Fellowship by Japanese Society for the Promotion of Science Lecture
  22. 1997 Series/Recent Advances in Cluster Science, May
  23. 1990 Conference Organizer and Chairman of Gordon Conference on Molecular and Ionic Clusters, first Gordon Conference held in Europe, Volterre, Italy, September 2-7, 1990
  24. 1989 Fulbright Senior Scholar Award
  25. 1988 Recipient of the ACS Award for Creative Advances in Environmental Science and Technology
  26. 1988-1998 Senior Editor of the Journal of Physical Chemistry
  27. 1987 Doktors Honoris Causa, University of Innsbruck, Austria
  28. 1986 Named Evan Pugh Professor of Chemistry, Penn State University
  29. 1986 U.S. Senior Scientist von Humboldt Award
  30. 1985 Elected Fellow of the American Association for the Advancement of Science
  31. 1985 Elected Fellow of the American Physical Society
  32. 1985 National Science Foundation Creativity Award
  33. 1983 Named Awardee of Senior Scientist Fellowship by Japanese Society for the Promotion of Science
  34. 1985 Lecture Series/Research on Clusters, March/April
  35. 1977 Sherman Fairchild Distinguished Scholar, California Institute of Technology (for senior faculty/researchers)

Selected Publications:

A.W. Castleman, Jr., "Cluster Structure and Reactions: Gaining Insights into Catalytic Processes," (Perspective) Catalysis Letters, 141, 9, 1243-1253 (2011).

A.W. Castleman, Jr., "From Elements to Clusters: The Periodic Table Revisited," Physical Chemistry Letters Perspective, 2, 1062-1069 (2011).

A. W. Castleman, Jr. and S. N. Khanna, “Clusters, Superatoms and Building Blocks of New Materials”, Feature Article for the Journal of Physical Chemistry, 113, 2664-2675 (2009).

G. E. Johnson and A. W. Castleman, Jr., “Clusters as Model Systems for Investigating Nanoscale Oxidation Catalysis”, Chemical Physics Letters, 479, 1-9 (2009).

D. P. Hydutsky, N. J. Bianco and A. W. Castleman, Jr. , “Photochemistry and Solvation of  HI(H2O)n Clusters: Evidence of Biradical Formation”, Chem. Phys. Lett., 476, 15-18 (2009).

G. E. Johnson, E. C. Tyo and A. W. Castleman, Jr., “Cluster Reactivity Experiments: Employing Mass Spectrometry to Investigate the Molecular Level Details of Catalytic Oxidation Reactions”, PNAS, 105, 18108-18113 (2008).

“Femtochemistry VII: Fundamental Ultrafast Processes in Chemistry, Physics, and Biology”, Editors: A. W. Castleman, Jr. and Michele L. Kimble, Elsevier: ISBN 0 444 52821 0 (2006).

A. W. Castleman, Jr. and  Puru Jena, “Clusters – A Bridge Across Disciplines: Environment, Materials Science, and Biology”,  PNAS, 103, 28,10554 ( 2006).

Puru Jena and A. W. Castleman, Jr., “Clusters – A Bridge Across Disciplines: Physics and Chemistry”, PNAS,  103, 28, 10560 (2006).

A. W. Castleman, Jr. and P. Jena, “Clusters – A Bridge Across Disciplines”, PNAS – (Invited perspective on the cluster field)- PNAS, 103, 28, 2006.

L. Poth, E. Wisniewski, and A. W. Castleman, Jr., "Cluster Dynamics: Fast Reactions and Coulomb Explosion," American Scientist, 90, 342-349, (2002).

Q. Zhong and A. W. Castleman, Jr., “An Ultrafast Glimpse of Cluster Solvation Effects on Reaction Dynamics,” Chem. Rev., 100, 4039-4057, (2000).


Matter of Nanoscale Dimensions

The realm of small dimensions often brings with it new phenomena, sometimes attributable to structure and bonding, while in other cases due to what is commonly called quantum confinement. The Castleman group is striving to bring new understanding to this challenging and important subject by employing the tools and principles from chemical physics to bridge an understanding and develop applications in a number of areas of modern chemical science. The methods employ high technology-molecular beams, flow reactors, ultrafast lasers, and sophisticated new mass spectrometer techniques. The targets are molecular complexes of significance in fields ranging from atmospheric and environmental science to catalysis, microelectronics, cluster assembled nanoscale materials, and hydrogen bonded complexes of biological molecules. Clusters are the media through which the explorations take place.

Professor Castleman and his students have devised numerous different schemes for producing weakly bound aggregates comprised of molecules, atoms, and/or ions of desired composition and size that can be subjected to detailed investigation. In order to determine the inherent properties and reactivity of these nanoscale systems, they typically study these in an unsupported fashion, either in a molecular beam or suspended in the carrier gas of a flow reactor. The bonding and molecular and optical properties of the cluster systems are ascertained using laser spectroscopy, while their reactivities are determined through a variety of techniques including femtosecond time-resolved laser pump-probe methods in some cases, and through investigations of their surface reactions using specially designed flow-tube reactor methods in others.

A few years ago, Professor Castleman and his students discovered a new class of molecular clusters termed Metallo-Carbohedrenes or Met-Cars for short. Because of their potential use as new electronic and optical materials, as well as possible value as new catalysts, they have attracted wide interest in the chemistry community. Work is under way to investigate their molecular properties, reactivity, and routes for their synthesis in the solid state.  This aspect of the work has been extended to developing superatoms as mimics of elements that can lead to a 3-D periodic table comprised of unique clusters that can serve as building blocks of new nanoscale materials.

Along the lines of exploring the physical basis for catalysis, the group is also engaged in a number of studies of the reactivities of metal compound clusters of widely varying composition and types, with particular attention given to oxygen transfer reactions. Investigations are also under way to learn how the small cluster building blocks lead to different morphologies of growing particles that are of interest in wide-ranging areas from photocatalysis to developing new cluster assembled nanoscale materials.

The vast majority of reactions of practical importance occur in liquids or on surfaces, yet from a molecular point of view they are far less well understood than reactions occurring in the gas phase. The Castleman group is working to lay a foundation for connecting information from the gas to the condensed phase through clusters. In this work, ultrafast lasers are used to excite various constituents of clusters with one laser beam, and probe the course of the ensuing reactions with a second one, all in the femtosecond time domain, thereby enabling actual observation of the making and breaking of bonds. The group has developed a unique method for interrupting and interrogating evolving intermediates in fast reactions using a novel Coulomb explosion technique. Work is in progress on studies of the spectroscopy and reactions of small solvated molecular functional groups, with the objective of learning more about the influence of varying degrees of solvation on their properties and reactivity. In addition, work is under way to develop new analytical techniques for selectively ionizing and sequencing large biological molecules, determining their molecular structures, and investigating the effects of ionizing radiation on matter.

Another major thrust is learning more about atmospheric chemistry through cluster research. It is well recognized that small aerosol particles, as well as ice crystals and cloud droplets, play an important role in the conversion of many atmospheric molecules. In recent investigations, the group has shed light on the fundamentals of heterogeneous reactions occurring on ice and water cluster surfaces, with attention to problems identified as important in the ozone hole observed in the polar regions of the stratosphere.

Much of the experimental work involves investigations of cluster dynamics and structures, and related computations into the properties of aggregates of nanoscale dimensions are made in support of the experiments. The promises of developing new materials with tailored properties abound.

Research Interests:


Aerosol formation: nucleation phenomena and reactions

Materials and Nanoscience

Devising unique materials using clusters as building blocks; studying element mimics and superatoms


Elucidating the properties of matter of small dimensions and related quantum phenomena


Ultra Intense Lasers and Using Femtosecond Techniques to Study Fast Reactions