Usually, isotopes are separated by exploiting the difference in nuclear weight. That difference is tiny, like sorting grains of sand that differ by one hundredth of a millimeter. The new method ignores weight and instead looks at the nucleus's rotation: its spin.
The laser hits the molecules twice with a short pause in between. For nuclei with zero spin (as in even isotopes), the second pulse brings everything back to square one, like an echo that exactly repeats the shout. But if the nucleus has spin (odd isotopes), an extra magnetic field arises inside it. This field disrupts the phase, and the echo doesn't close — some molecules remain in an excited state. These can be collected.
Under normal conditions, where molecules collide, the method yields enrichment above 90% in a single pass. No need to build cascades of thousands of stages, a single laser setup suffices.
Nuclear spin was discovered through the hyperfine splitting of spectral lines, as if the note 'A' were slightly altered in pitch by a tiny magnet inside the atom.
In the novel 'The Martian', plutonium isotopes serve as an energy source for the Mars rover — perhaps in the future, they will be extracted using just such a laser method.