Helen Leung's Research Interests

 

My research aims to understand intermolecular interactions due to van der Waals forces between nonchemically bonded molecules. Although van der Waals forces are much weaker than chemical forces, the immense number of pairwise interactions due to these intermolecular forces is responsible for the structures and functions of chemical and biological systems. Despite the ubiquity of these forces and their importance, however, they are still not completely understood, and the work in my group addresses this gap.

Because van der Waals forces are usually masked by chemical forces, they must be isolated before they can be effectively studied. This can be done by molecular beam methods, which generate molecular complexes that owe their very existence to van der Waals forces. The intermolecular forces determine the structures and affect the electronic environments of the complexes. Thus, the characterization of molecular properties, which can be efficiently accomplished using spectroscopic techniques, provides valuable information on the operative forces. My group utilizes a high resolution, pulsed molecular beam, Fourier transform microwave spectrometer to obtain the rotational spectrum of a complex that can then be analyzed to yield the desired molecular information.

My group has studied a series of nitrous oxide-containing complexes to examine how van der Waals forces perturb the electronic distribution of the subunits. Recently, I have begun a collaboration with Professor Mark Marshall seeking to understand the effects of electron density on complex geometry, and we have chosen as our systems haloethylene-containing complexes. Our additional projects include hydroxide radical-containing complexes (for this, the collaboration extends to include Professor Kenneth Leopold at the University of Minnesota) and other reactive complexes to gain further understanding of the role of van der Waals forces in reaction pathways.  A list of species studied by my group (some in collaboration with other groups) is listed below.  Undergraduate investigators are underlined and class years for Amherst students are provided.

 Molecular Species

Investigators

Articles/Status

Ar-N2O

Deepa Gangwani, Jens-Uwe Grabow, Helen O. Leung

Chemical Communications 1996, 2525 (1996); Journal of Molecular Spectroscopy 184, 106 (1997)

HCCH-N2O

Rebecca A. Peebles, Sean A. Peebles, Robert L. Kuczkowski, Helen O. Leung

Chemical Communications 1996, 2525 (1996); Journal of Chemical Physics 107, 2232 (1997); Journal of Physical Chemistry A 103, 10813 (1999)

CO2-N2O

Helen O. Leung, Mark D. Marshall

Journal of Chemical Physics 108, 3955 (1998); Journal of Molecular Spectroscopy 196, 149 (1999)

N2-N2O

Helen O. Leung

Journal of Chemical Physics 110, 4394 (1999)

OCS-N2O

Anne M. Osowski, Olayinka A. Oyeyemi, Helen O. Leung

Journal of Chemical Physics 114, 4829 (2001)

OD-N2

Maria Tsiouris, Ilana B. Pollack, Helen O. Leung, Mark D. Marshall, Marsha I. Lester

Journal of Chemical Physics 116, 913 (2002)

OD-CO

Ilana B. Pollack, Maria Tsiouris, Helen O. Leung, Marsha I. Lester

Journal of Chemistry Physics 119, 118 (2003)

HF-N2O

P. I. Abruña, M. B. Bianchi, O. M. Ibidapo, Helen O. Leung

Journal of Molecular Spectroscopy 222, 3 (2003)

HCl-N2O

Winn T. Cashion  ‘05, Katharine K. Duncan ‘06, Christine L. Hagan ‘05, S. Joo, Helen O. Leung

Journal of Chemical Physics 121, 237 (2004)

OH-H2O

Carolyn S. Brauer, Galen Sedo, Eric K. Grumstrup, Erin Dahlke, Shenghai Wu, Kenneth R. Leopold, Mark D. Marshall, Helen O. Leung, Donald Truhlar

Chemical Physics Letters 401, 420 (2005); Journal of Chemical Physics 129, 104304 (2008)

1,1-Difluoroethylene-HCCH

Helen O. Leung, Mark D. Marshall

Journal of Chemical Physics 125, 154301 (2006)

1,1-Difluoroethylene-HF

Tasha L Drake ‘09, Tadeusz Pudlik ‘09, Nazir Savji ‘08, Daniel W. McCune ‘09, Helen O. Leung, Mark D. Marshall

Journal of Chemical Physics131, 204301 (2009)

1,1,2-Trifluoroethylene-HF

Helen O. Leung, Mark D. Marshall

Journal of Chemical Physics 126, 114310 (2007)

1,1,2-Trifluoroethylene-HCCH

Winn T. Cashion ‘05, and V. L. Chen’08, Helen O. Leung, Mark D. Marshall

Journal of Chemical Physics 128, 064315 (2008)

1,1,2-Trifluoroethylene-HCl

Margaret R. Ray ’08, Justin T. Kang ’08, Helen O. Leung, Mark D. Marshall

Journal of Physical Chemistry A 114, 10975 (2010)

trans-1,2-Difluoroethylene-HF

Brent K. Amberger ‘08, Helen O. Leung, Mark D. Marshall

Journal of Chemical Physics 131, 204302 (2009)

SnS

Helen O. Leung, Mark D. Marshall

Journal of Molecular Spectroscopy 265, 52 (2011)

2,3,3,3-Tetrafluoropropene

Benjamin Q. Scheetz ’12, Jonathan E. Thaler ’12, John S. Muenter, Helen O. Leung, Mark D. Marshall

Journal of Molecular Spectroscopy 266, 37(2011)

1-Chloro-1-fluoroethylene

Andrew L. Vasta ‘08, Norman C. Craig, Helen O. Leung, Mark D. Marshall

Journal of Molecular Spectroscopy 253, 116 (2009)

1-Chloro-1-fluoro-ethylene-HCCH

David Grimes ’09, Helen O. Leung, Mark D. Marshall

Journal of Chemical Physics, 134, 034303 (2011)

1-Chloro-1-fluoroethylene-HF

Aaron T. Bozzi ’10, Paul M. Cohen ’11, Mable Lam ’12, Helen O. Leung, Mark D. Marshall

Journal of Molecular Spectroscopy 267, 43(2011)

(E)-1-Chloro-2-fluoroethylene-HF

Alex J. Lee ‘09, Helen O. Leung, Mark D. Marshall

Manuscript in preparation

(E)-1-Chloro-1,2-difluoroethylene-HF

Aaron T. Bozzi ’10, Helen O. Leung, Mark D. Marshall

Manuscript in preparation

Ar- (Z)-1-chloro-2-fluoroethylene

Catherine E. Calvert ‘09, Helen O. Leung, Mark D. Marshall

Journal of Molecular Spectroscopy 280, 97(2012)

Ar-cis-1,2-difluoroethylene

Jessica L. Mueller ’13, Brent K. Amberger ‘08, Helen O. Leung, Mark D. Marshall

Journal of Chemical Physics 139, 134303 (2013)

Ar-2-chloro-1,1-difluoroethylene

Joseph P. Messinger ’14, Gregory S. Knowlton ’15, Kathryn M. Sundheim ’15, Jasmina Cheung-Lau ’07, Helen O. Leung, Mark D. Marshall

Manuscript in preparation

Ar- (E)-1-chloro-1,2-difluoroethylene

Hannah Tandon ’16, Joseph P. Messinger ’14, Eli Mlaver ‘14, Helen O. Leung, Mark D. Marshall

Experiment in progress

Vinyl chloride-HCCH

Fan Feng ‘13, Helen O. Leung, Mark D. Marshall

Journal of Physical Chemistry A 117, 13419 (2013)

Vinyl chloride-HF

Helen O. Leung, Mark D. Marshall

Manuscript in preparation

Vinyl chloride-HCl

Joseph P. Messinger ’14, Helen O. Leung, Mark D. Marshall

Experiment in progress

(E)-1-chloro-1,2-difluoroethylene-HCCH

Eli Mlaver ‘14, Helen O. Leung, Mark D. Marshall

Experiment in progress