Chandra Prayaga

Polarization Sensitive CARS Investigations of Controlled Molecular Rotations

The emerging field of nanotechnology requires new methodologies to be developed in order to address the needs of fabrication, manipulation, control, and measurement of motions of molecules and devices on the nanoscale. Optical excitation and control of translational, vibrational, and rotational motions can offer a unique way to achieve the desired goals by using a sequence of short laser pulses, e.g., tuned to initiate certain nuclear motions of well studied photo active proteins (e.g. PYP or Rhodopsin) or engineered larger molecular structures. Measuring nuclear motions requires structurally sensitive spectroscopy methods, and therefore spontaneous Raman and coherent Raman spectroscopies can be applied to qualitatively test and quantitatively measure such motions.Polarization Sensitive Resonance Coherent anti‐Stokes Raman Spectroscopy (PSCARS), steady state or time‐resolved, can measure controlled dipole moment reorientation through the anisotropic third order nonlinear optical susceptibility. The measur...

Preparing Content-Rich Learning Environments with VPython and Excel, Controlled by Visual Basic for Applications

A simple interface between VPython and Microsoft (MS) Office products such as Word and Excel, controlled by Visual Basic for Applications, is described. The interface allows the preparation of content-rich, interactive learning environments by taking advantage of the three-dimensional (3D) visualization capabilities of VPython and the GUI capabilities of MS Office. MS Office provides the user interface for data input. The data are stored in a text file, which is read by VPython and used in 3D graphical simulations. Use of the interface is illustrated by working through an example of the motion of a charged particle in a magnetic field. A user interface designed in Excel allows the student to input data on the charge and the mass of the particle, the initial conditions and the magnetic field. The data are then saved in a text file. VPython reads the data and renders the 3D graphics visualization of the motion. Interactivity is ensured since the student can change the data and directly observe the changes in motion.