 |
| Born
Flushing, New York, 1959. |
| Massachusetts
Institute of Technology, B.S., 1981. |
| University
of California, Berkeley, Ph.D., 1985. |
| University
of Wisconsin, Postdoctoral Research Associate, 1985-86. |
| The
University of Chicago, Professor, 1987-. |
| |
| Accolades |
| 2002
Fellow, American Physical Society. |
| 1993
Llewellyn John and Harriet Manchester Quantrell Award for Excellence in
Undergraduate Teaching, The University of Chicago. |
| 1992
Alfred P. Sloan Fellow. |
| 1989
Camille and Henry Dreyfus Foundation Teacher-Scholar. |
| 1988
National Science Foundation Presidential Young Investigator. |
| 1987
Office of Naval Research Young Investigator. |
| 1986
Camille and Henry Dreyfus Distinguished New Faculty in Chemistry Grant. |
|
|
| Laurie
J. Butler |
| Professor |
|
|
| |
| Research
Interests: |
| Our
research investigates the fundamental inter- and intramolecular forces
that drive the course of chemical reactions. To experimentally probe
the detailed molecular dynamics, both nuclear and electronic, during a
chemical reaction we use a combination of molecular beam reactive
scattering and laser spectroscopic techniques. Traditionally,
predicting rate constants and microscopic dynamics has relied on
statistical transition state theories or, in smaller systems, quantum
scattering calculations on a single adiabatic potential energy surface
that provides the barriers to each reaction. However, a reaction
evolves on a single potential energy surface only if the Born
Oppenheimer separation of nuclear and electronic motion is valid. Much
of our recent work investigates classes of important chemical reactions
where the breakdown of the Born-Oppenheimer approximation (the
inability of the electronic wavefunction to readjust rapidly enough
during the nuclear dynamics) near the transition state alters the
dynamics and markedly reduces the reaction rate. The studies test the
predictions of emerging quantum theories on nonadiabatic reaction
dynamics in small systems and develop an intuitive framework for
understanding chemical reaction dynamics in more complex organic and
inorganic reactions not yet accessible to precise quantum calculations.
|
| |
| As an
example, our recent work on nitric acid and other important atmospheric
species seeks to understand from first principles quantum mechanics why
some chemical products are produced and not others. In the
photodissociation of nitric acid two chemical bonds may break,
producing OH+NO2 and HONO+O respectively. The
ability of the electronic wavefunction to change along the reaction
coordinate, particularly the orientation of the radical OH p electron's
orbital, plays a critical role in determining what products are formed.
Our early molecular beam experiments showed that nonadiabatic
recrossing of the transition state plays a dominant role in determining
the branching between chemical bond fission channels, reversing the
expected branching between C-Br and C-Cl fission in the Br(CH2)nCOCl.
Suppressing rapid intramolecular electronic energy transfer allows you
to preferentially cleave a selected chemical bond. Our experiments and
supporting ab initio calculations elucidate the intramolecular distance
and conformation dependence of nonadiabatic recrossing of the reaction
barriers in the competing reaction channels. |
| |
| Other
experiments use molecular photodissociation to directly access both the
upper and lower adiabatic potential energy surfaces, respectively, near
the transition state region of a excited state bimolecular reaction to
probe the influence of nonadiabatic coupling in chemical reaction
dynamics. Our molecular beam photofragmentation and emission
spectroscopy experiments and collaborative theoretical work on CH3SH
investigated how accessing different regions of the CH3S
+ H → CH3+SH reactive potential energy
surfaces changes the branching between the S-H and C-S bond fission
channels and how nonadiabatic coupling influences the dynamics. In this
system and in H2S, we used the technique of
emission spectroscopy of dissociating molecules to investigate the
dynamics which occurs during the subpicosecond dissociation event,
providing a key link between the absorption spectrum and the final
product quantum states. |
| |
| We have
recently introduced a method for investigating the competing
unimolecular dissociation channels of isomerically-selected radicals as
a function of internal energy in the radical. Radical intermediates
play a key role in a wide range of chemical processes, yet many key
isomeric radical intermediates elude direct experimental probes. Our
experiments photolytically produce from an appropriate precursor a
selected radical isomer and disperse the radicals by their neutral
velocity imparted in the photolysis, thus dispersing them by internal
energy. For the unstable radicals, they then measure the branching
between C-C and C-H fission products via tunable VUV photoionization of
products dispersed by their velocity. This offers the unprecedented
ability to measure the branching between isomeric product channels as a
function of internal energy in the dissociating radical isomer on the
ground state potential energy surface. |
| |
| Selected
References |
| |
| Dissociation Dynamics of the Methylsulfonyl Radical and its Photolytic Precursor, J. Chem. Phys., 131, 044305 (2009). |
| Investigation of the O + allyl addition/elimination reaction pathways from the OCH2CHCH2 radical intermediate, J. Chem. Phys., 129, 084301 (2008). |
| Determination of the Barrier Height for Acetyl Radical Dissociation from Acetyl Chloride Photodissociation at 235 nm Using Velocity Map Imaging, J. Phys. Chem. B, 112, 16050 (2008). |
| Unimolecular Dissociation of the CH3OCO radical: An Intermediate in the CH3O + CO Reaction, J. Chem. Phys., 110, 1625 (2006) and Fig. 9 in J. Phys. Chem. A, 111, 1762 (2007). |
| Chemical Reaction Dynamics Beyond the Born-Oppenheimer Approximation, Annu. Rev. Phys. Chem., 49, 125-171 (1998). |
| The Influence of Local Electronic Character and Nonadiabaticity in the Photodissociation of Nitric Acid at 193 nm, J. Chem. Phys., 107, 5361 (1997). |
| Photodissociation Dynamics, J. Phys. Chem., 100, 12801 (1996). |
| Dissociation Dynamics of CH3SH at 222, 248, and 193 nm An Analog for Probing Nonadiabaticity in the Transition-State Region of Bimolecular Reactions, J. Chem. Phys., 98, 2882 (1993). |
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Physical Chemistry 