Successful techniques exist for bringing atoms down to really cold temperatures, into the regimes where the most exotic collective quantum phenomena appear. However, those same techniques don’t work for polyatomic molecules—those consisting of three or more atoms. This is a bit frustrating for physicists, since molecules have the potential to exhibit some truly wild quantum effects: parity violation (processes that depend on which direction they occur), quantum chemical effects, and—hopefully—new phenomena which we don’t expect. A new experiment has succeeded in using three different types of light in tandem to bully molecules down to cold temperatures, a process known as Sisyphus cooling.
For this reason, the researchers in the present study turned to a more elaborate technique, where multiple processes were utilized in succession to cool the molecules. The experimenters sent a stream of molecules into a trap made from standing microwaves crossed with an infrared laser beam. The trap itself consisted of a sort of radio antenna; by varying the frequency of the radio waves, the researchers could extract energy from the molecules rapidly.
The combination of the excitation with a laser and the jostling by radio waves boosted the energy state of the molecules slightly, but they lost even more energy when coming down, resulting in ever colder temperatures. This virtual harassment to produce ultracold temperatures gives the process its name of Sisyphus cooling, referring to the Greek myth of a wicked king punished in Hades to repeat a single task forever. [Read more....]