Physics · the experiment
Switch off the superatom
Twelve silver atoms around one tungsten atom, and a lone electron in a round shell. Tune the laser until the cluster falls silent, then redo the calculation that explains it.
1 · Why zero, not just a dip?
Beginner
Why can the electron in the 2S shell stop coming out entirely, when elsewhere only a dip is seen?
2 · Switch off the ring
Intermediate
At the centre of the gap, near 2.3 eV, how much energy does the escaping electron carry?
Tune the laser energy until the ring of electrons on the detector almost goes out.
3 · Cancel the integral
This is the article's idealised sphere (figure 1), not the real cluster: radius 20 bohr (about one nanometre), simple outgoing wave. The plot traces the orbital × the p-wave × r³.
Expert
The idealised sphere goes out at 1.87 eV, the real Ag12W⁻ near 0.85 eV. What moves the zero?
Tune the electron's energy until the red and blue areas cancel.
4 · Where the electrons go
The number β sums up the direction in which electrons fly out: it is 0 when they fly out equally in all directions and 2 when they leave mostly along the direction in which the laser light's electric field oscillates. It reaches 2, the limit for an atom, around 2.7 eV; in the gap, it drops to nearly zero.
Expert
Why does β collapse in the gap?
Superatom switched off
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