The Chronister Group: Research
Our research utilizes ultrafast pulses of light (~10-12 sec) to make time-resolved measurements of the fast
changes which occur when molecules are excited by the absorption of light.
We build ultrafast lasers and utilize high power picosecond (and subpicosecond)
pulses of light to excite and probe molecular changes. We perform very low
temperature measurements (e.g. 1.1 K using liquid helium dewars and cryostats)
as a means of minimizing unwanted thermal effects. We also utilize diamond
anvil techniques to generate extreme high pressure conditions. Currently
we are studying the chemical dynamics (and novel applications) of a variety of
molecular solids, such as pure molecular crystals, impurity doped molecular
crystals and organically doped inorganic glasses.
- The Dynamics of Molecular Solids at High
Pressure.
Time-resolved coherent spectroscopic studies of
energy relaxation in molecular solids under high pressure conditions (up to
100,000 atmospheres) are being used to probe the nature of molecular
interactions. Diamond anvil cells are used to produce the high pressures
necessary to alter intermolecular distances, which enables us to make
relaxation measurements as a function of the intermolecular interaction
strength. Furthermore, time-resolved coherent spectroscopic techniques
are used to provide unique high resolution probes of molecular dynamics under
these extreme conditions. (Supported by the National Science
Foundation).
PowerPoint
Presentation
- The Dynamics of Organically Doped Inorganic
Sol-Gel Glasses, and Development of Sol-Gel Clad Fiber Optic
Sensors.
Sol-gel glasses are formed at room temperature by a
slow inorganic polymerization reaction. This unique synthesis allows the
processing of organically doped materials which hold promise as novel
materials for a variety of optical and electronic applications (e.g. chemical
sensors, solid state dye lasers, photochromic devices and erasable optical
memory media). We incorporate delicate organic molecules into a variety
of inorganic glasses (e.g. silicate, aluminosilicate, transition metal oxides,
etc.) and probe the optical response (e.g. fast optical switching) and
molecular dynamics (e.g. rotational motion within the glass) by a variety of
time-resolved spectroscopies. Sol-gel clad optical fibers are also being
investigated as novel chemical sensors. (Supported by the Environmental
Protection Agency and the Army Research Office).
PowerPoint
Presentation
- Ultrafast Vibrational Relaxation in Unique
Molecular Solids
These studies currently focuses on molecules
with energy bottlenecks (i.e. long lived vibrational modes which can store
energy). Such studies of how molecules dispose of excess energy are important
for understanding of how molecular dynamics are related to chemical reactions.
(Supported by the Petroleum Research Fund).
- Transient
Optical Grating Measurements of Sound Velocities at Simultaneous High Pressure
and High Temperature.
Optically induced acoustic waves are
produced by stimulated Brillouin scattering on a variety of geologically
relevant materials in a high pressure diamond anvil cell. (Supported by
the Institute of Geophysics and Planetary Physics).
PowerPoint
Presentation
