Spent the rest of the day puzzling through some papers. “What,” you ask, “was puzzling about them?” Well I’m glad you asked. Either Schwentner has left out some crucial bits of information, or has found a way to violate causality, that pesky little thing that says the cause has to preceed the effect. In laser experiments this means you have to hit the molecule with a pulse before the effect you are looking for can be observed. Fine. Well the pump-probe spectra of Cl2 in Ar shows some modulation for negative time delays.
Listen: A real-world analogy for pump-probe spectroscopy would be eating a huge meal, taking a laxative, and examining the output to compare with the input. We start off with food, we do something to it (eat it and wash it out with the laxative), and we examine what it looks like in the end to try to determine what happened to it while being digested. Now if we take the laxative BEFORE we eat the food, nothing happens. This would be similar to having a negative time delay in a pump-probe (eating-laxative) experiment.
This paper shows a signal for negative time delays. It’s like…well you get the picture. On the plus-side I’ll be referring to pump-probe experiments as eating-laxative experiments from now on. So I have that going for me.