Research Progress

Optical Experiment

1^st Beam Time:

-Found time and spatial overlap of the three probe beams with the pump beam, and overlap with the gas jet

-Aligned molecules using optical experiment

-Unable to align Iodobenzene molecules

-The gas jet is a jet of helium, which is seeded with the type of molecule one wants to study. We did not have enough Iodobenzene in the jet to align.

-Proof of this is that when we looked at the revivals in the alignment graphs, we saw revivals for helium, not Iodobenzene. While we will get some background alignment for helium, the signal for Iodobenzene alignment was very weak.

2^nd Beam Time:

-Replace gas jet and use more Iodobenzene, then try to align Iodobenzene again and study the revivals

VMI Experiment

1^st Beam Time:

-Found time of flight and autocorrelation

-Once again we did not see a strong Iodobenzene signal, so we decided to replace the gas jet and flange to the pump

-Before this beam time, we put more Iodobenzene in the jet, so we knew that we had more than enough Iodobenzene

-The only other possibility, was that the jet was leaking

-After replacing and cleaning the jet and flange, we saw a stronger signal of Iodobenzene, but weak alignment

-One possibility is that the pump beams’ pulse duration was too short or that the probe beams’ pulse duration was too long

-Pump beam duration too shortàionization

-Probe beam duration too longàcount size too small

-Another possibility is that the pump/probe did not have the correct power ratio

-We tried raising and lowering the power in both the pump and the probe beams, but could not get an alignment above 0.62

-We built another autocorrelation for all the beams and measured the pulse duration and pulse width of both the probe and the pump

-Since we want the pump beams to be greater in width then the probe beam, so that the probe beam probes only where the molecules have been pumped

2^nd Beam Time:

Programming:

In addition to helping with the experiments, I have worked with LabVIEW and MATLAB. I wrote a program which calculates the Fourier transform and inverse Fourier transform of any Gaussian shaped pulse given the coefficients of refraction for the sellmeier equation of the material(s) it passes through. We used this program to predict how the laser pulse would be affected after passing through the BBO crystal, calcite, ½ wave plate, and other materials.

In MATLAB, I worked on a program that one of my graduate students wrote. I wrote a short code to save all the plots the program produced and to read the inputs from another file instead of directly plugging in values. This program is used to predict the alignment and orientation of a linear rotor molecule (such as CO). I used this program, after some changes, as a rough estimate of the alignment and orientation of Iodobenzene. I also wrote a short program that would calculate the Fourier transform of the data I would call from the linear molecule program.