TrA Data collection

Explaining how we collect data with our transient absorption spectrometer is often very difficult.

Many people in a chemistry lab know how to collect a UV/Vis spectrum of a ground state molecule's absorbance of light at different wavelengths. However, transient absorption spectroscopy (TrA) looks at the excited molecule's spectrum and how it changes in time after its initial excitation.

These three-dimensional graphs contains so much more information than a typical absorption measurement. The transition energies are shown in the spectrum and how these change in time can be related to the kinetics. Together, these are what makes TrA so powerful - the ability to understand how the energetics of excited molecules change with time.

In the lab we collect the data by collecting the spectrum of the excited molecule using a probe pulse of white light (we also have to subtract the response without the pump). We can delay the probe relative to the pump and collect a spectrum at a later time. This is how we then build up the 3D surface.

The animation shows a TrA spectrum (which I made up). I masked the data, saved a picture and then used ImageJ to make the GIF. I will upload the code after my exams.