https://phys.org/news/2018-07-ultracold-atoms-ultrafast-lasers.html

Ultrashort laser pulses can be so intense that they rip atoms apart. This process is called strong-field ionization and the details depend on the energy and color of the laser light. Up until now, it was not always possible to know which ionization regime dominates. The scientists have now succeeded in observing this in detail by using ultracold atoms. As there is hardly any atomic motion after the ionization process, it is possible to accurately measure the regimes.

The scientists used laser light to cool rubidium atoms to ultracold temperatures of 100 nanokelvins, only slightly above absolute zero temperature of -273.15° Celsius. An intense ultrashort laser pulse illuminated parts of the cloud of rubidium atoms for a very short time of 215 femtoseconds (a femtosecond is one millionth of one billionth of a second) and ionized a fraction of the atoms. The remaining atomic density was imaged onto a camera so that the amount of ionized atoms could be accurately measured.