Fun with spins
Contents
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)
This is one of the listed points in: Piezochemical mechanosynthesis#Surprising facts
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)
(TODO: answer questions below – eventually explain and illustrate results)
Perhaps open questions are:
- Which heavy elements to use for speeding up reactions by speeding up inter system crossing?
- Which geometries to place these atoms on the tooltips ideally? (proximity, overlap, reaction participation, orientation, ...)
- How important is this: How big is the effect and how do different reactions vary?
Related:
Nanosystems (from glossary) about Inter system crossing ...
- ... and energy dissipation, 224
- ... in pi-bond torion, 231
- ... radical coupling, 215
- ... rates of, 197, 216
- ... and reaction reliability, 210
- (also noted on page 235 top)
Electron spins
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)
Nuclear spins
A rare case where nuclear spins have a huge (physical) effect are the nuclear spin isomers of hydrogen.
Nuclear spins usually have only minor effect on physical and chemical properties.
But they are very useful for analytic (and in the future maybe computation) purposes.
Generally
Magnetism behaves deeply quantum mechanically even at quite high temperatures (meaning room temperature)
and that across size scales spanning several atoms.
This is making crude approximations harder (or impossible).
Related
- Mechanically stable electronically excited states
- Polyaromatic pigments, F-centers in gemstones, ...See: color emulation
External links
- Magnetic refrigeration – Magnetocaloric effect – (Related: Entropomechanical converter)
- (drifting off-topic: the corresponding Electrocaloric effect)
