Fun with spins
Spin in piezochemical mechanosynthesis
Intersystem_crossing:
This can lead to the problem in piezochemical mechanosynthesis that when pressing moieties together too fast to hard,
the reaction can actually lock up and slow down rather than speed up. (wiki-TODO: check details)
Spin flips in tool-tips (to create an anti-parallel bonding singlet state) can be influenced by
nearby massive atoms with high spin orbit coupling.
(wiki-TODO: find out how that is supposed to be working)
Oxygen has as its unexcited state the triplet state with unpaired parallel electron spins
(meaning it is a stable diradical). This is quite unusual.
The excited state of oxygen is singlet oxygen with paired antiparallel spins.
Singlet oxygen is quite metastable leading to fluorescence (red colored)
Ortohelium is heliums ground state (with necessarily paired antiparallel spins).
Parahelium with unpaired parallel spins (and necessarily one electron in the 2s shell)
is surprisingly metastable (despite being excited by a whopping 19,8 eV). There is a "forbidden" state transition.
(Wikipedia: Helium atom)
A rare case where nuclear spins have a huge (physical) effect are the nuclear spin isomers of hydrogen.
Related
- Mechanically stable electronically excited states
- Polyaromatic pigments, F-centers in gemstones, ...See: color emulation
