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why does bombarding tightly-packed rubidium-87 atoms with lasers cool them to minus 273.15 degrees Celsius?
by smhost 8y ago
why does bombarding tightly-packed rubidium-87 atoms with lasers cool them to minus 273.15 degrees Celsius?
- ars 8y agoThe simplest way to explain it is this: Atoms can only absorb very specific and exact frequencies of light. But because the atoms are moving, the frequency of light, as seen by the atom, varies a lot. If you only shine light that is slightly below the lowest frequency of light the atom can absorb, only those atoms that are moving toward the light (and thus "see" a slightly higher frequency) are able to absorb that light. Then the atom emits that light - which is always at the exact frequency. In the process you basically "steal" energy from the atoms motion, and emit it back out as ever so slightly higher frequency light. Since the atoms are now moving slower they are colder. You keep doing this until you've gotten as much out of the process as you can.
- BurningFrog 8y agoSo do the moving atoms "see" different frequencies because of doppler effects, or something else?
- ars 8y agoYes, doppler effect.