2D-IR spectroscopy is a little bit complicated to explain in a few words. With 2D-IR spectroscopy we can measure the dynamics of a molecule by measuring the vibrational frequency twice.
Still with me? Okay… to do this we take an ultrashort laser pulse and split it into three. We then delay the pulses relative to each other and then focus them on the sample. The three pulse come in from three different directions and the signal is emitted in a fourth direction. To actually measure the signal we need to…
Anybody still there? Well, I made an animation of the setup. I hope it is more illuminating!
I’m quite proud of the video, but it is not entirely accurate. We obviously don’t throw in beam splitters at the speed of light :) And did you notice that at 4 seconds the light travels through the box? In the setup there is a hole there.
The biggest problem is that I want to show the physical size (height and width) of the pulses, so you can see that they are focussed on the sample, but that I also need to show the lower intensity of the signal. I could make the signal darker, but that makes it difficult to see (especially when using a beamer during a presentation, like my PhD defense). Instead I opted to use the height and width of the signal to show the lower intensity, even though the physical size is the same as the three pulses…
Despite this I think the animation gives a nice idea of the setup, even for me, after so many years working on it. We have a tracer in the setup that shows the beam paths, but we obviously don’t see the individual pulses going through the setup (the path length in the setup is about 1.5 meters, the pulses take about 5 nanoseconds to travel that distance). This animation nicely shows the relative distances between the pulses.
The animation is made using Blender. Because I’m more of a programmer than an artist I used Python scripting to generate the animation. I’m not saying it is exactly easy to do, it took me one or two weeks to program it. It then took about six hours to actually render the animation and then a few hours to put the whole thing together in Final Cut Pro.