Research Projects

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. 

1.  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).  [Presentation - "Research Projects #1" pull-down menu]

2.  Mechanochemical Changes Utilizing Dynamic Diamond Anvil Cell Spectroscopy.

Impulsive high-pressure changes are used to induce chemical and physical changes (e.g. mechanochemistry, protein folding, solid-solid phase transitions, etc.) which can be probed by time-resolved spectroscopy.  (Supported by the National Science Foundation and the ACS Petroleum Research Fund).  [Presentation - "Research Projects #2" pull-down menu]

3.  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).   [Presentation - "Research Projects #3" pull-down menu]

4.  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. (Previously supported by the Petroleum Research Fund).  [Presentation - "Research Projects #4" pull-down menu]

5.  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 geologically relevant materials in a high pressure diamond anvil cell.  (Supported by the Institute of Geophysics and Planetary Physics).  [Presentation - "Research Projects #5" pull-down menu]