Aug
02

Instrument issues || July

One morning a couple of weeks ago I went to calibrate the Raman spectrometer I’d been using, the same way I always did before starting to take scans. The main peak in the spectrum of my standard had an intensity that was more than an order of magnitude lower than I expected. Looking back at spectra I’d saved from some of my more recent calibrations to compare to the extremely low intensity one I’d just collected, I discovered that I’d inaccurately determined the intensity of a couple of them. I combed through all of the calibrations I’d recorded over the course of the summer to see whether I’d made the same mistake on any of them.  A bigger problem soon emerged – as I moved backward in time the peak heights in the calibration were steadily growing. I plotted the intensities against time and found a strongly linear pattern. The decline in intensity while recording spectra of the same standard under the same conditions suggests that the laser that serves as the excitation source in the instrument is dying.

Luckily, the Applied Research Center (ARC) has a Raman spectrometer, and I have been able to reserve time on that instrument and continue collecting data. My instrument dying is still a setback and makes some of the work I’ve done this summer less useful. Nonetheless, this entire process has been much less concerning than it would have been if I didn’t have access to resources like the ARC, and I’ll be able to continue in my intended direction as I move into the fall semester.

The issues with the Raman spectrometer also haven’t interfered with my progress on the atmospheric chemistry side of this project. I’ve continued exposing samples of artist materials to ozone to explore the concentrations and lengths of exposure that will produce the fading processes we intend to investigate. Particularly dramatic results came with the exposure of dye solutions sprayed onto TLC plates – as Grosjean, et al. suggest in “Fading of Alizarin and Related Artists’ Pigments by Atmospheric Ozone: Reaction Products and Mechanisms,” the colorants we’ve looked at fade much faster as dye solutions on silica than as neat compounds on glass.

As is often the case, the beginning of summer research feels like ages ago but I still can’t quite believe how close we are to the end of it. I’m looking forward to having a bit of time off before coming back in the fall, reenergized and ready to tackle the integration of all of the different pieces I’ve been working on this summer!

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