Inter system crossing - Revision history

Apm: /* Side-notes to spinning flips via ISC */

2021-07-01T09:58:44Z

Side-notes to spinning flips via ISC

← Older revision		Revision as of 11:58, 1 July 2021
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	* Beside "spin flipping" there is also "spin rephaseing" as a possible transition (precession speed ...) ???		* Beside "spin flipping" there is also "spin rephaseing" as a possible transition (precession speed ...) ???
	* This topic is related to spectroscopy and optical effects		* This topic is related to spectroscopy and optical effects
			<br>
			----

	= Inter system crossing in (piezochemical) mechanosynthesis =		= Inter system crossing in (piezochemical) mechanosynthesis =

Apm at 09:57, 1 July 2021

2021-07-01T09:57:42Z

← Older revision		Revision as of 11:57, 1 July 2021
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	* Singlet state (paired) to low lying triplet state is undesired		* Singlet state (paired) to low lying triplet state is undesired
	To avoid that		To avoid that
	* either (conservatively) get the energy gap up to above 145zJ (= k300Kln(10^15)]		* either (conservatively) get the energy gap up to above 145zJ ( = k * 300K * ln(10^15) )
	* or (weaker prerequisite) get the accumulated ramp-on ISC transition rate to a probability above ln(P_err) prior <br>to theΔV_s,t point where the geometry is no longer suitable for bond formation		* or (weaker prerequisite) get the accumulated ramp-on ISC transition rate to a probability above ln(P_err) prior <br>to theΔV_s,t point where the geometry is no longer suitable for bond formation

Apm: /* Related / added link to yet unwritten page about Electronic transitions

2021-07-01T09:01:49Z

Related: added link to yet unwritten page about * Electronic transitions

← Older revision		Revision as of 11:01, 1 July 2021
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	* [[Quantum mechanics]]		* [[Quantum mechanics]]
	* [[Photonics]]		* [[Photonics]]
			* [[Electronic transitions]]

	= External links =		= External links =

Apm: /* Related / added Quantum mechanics * Photonics

2021-07-01T09:00:55Z

Related: added * Quantum mechanics * Photonics

← Older revision		Revision as of 11:00, 1 July 2021
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	* [[Mechanosynthesis]]		* [[Mechanosynthesis]]
	* [[Fun with spins]] – influencing spins by ligand-fields (crystal-fields) rather than spin-orbit coupling		* [[Fun with spins]] – influencing spins by ligand-fields (crystal-fields) rather than spin-orbit coupling
			* [[Quantum mechanics]]
			* [[Photonics]]

	= External links =		= External links =

Apm: /* Relativistic quantum mechanics saving the day */ added formula – and questions about "external heavy atom effect"

2021-07-01T08:58:59Z

Relativistic quantum mechanics saving the day: added formula – and questions about "external heavy atom effect"

← Older revision		Revision as of 10:58, 1 July 2021
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	<small>(these fall out of the Dirac equation – the relativistic generalization of the Schrödinger equation)</small> <br>		<small>(these fall out of the Dirac equation – the relativistic generalization of the Schrödinger equation)</small> <br>
	One gets a spin-orbit coupling energy term in the Hamiltonian. Exactly what we want. <br>		One gets a spin-orbit coupling energy term in the Hamiltonian. Exactly what we want. <br>
	In the non-relativistic picture this effect can be fudged in as a perturbation term.		In the non-relativistic picture this effect can be fudged in as a perturbation term. Spin orbit coupling term (SO).

	{{~~Wikitodo\|add formula~~}}		<math> H_{SO} = - \frac{Z^4 e^2}{8 \pi \epsilon_0 m_e^2 c^2} \vec l \cdot \vec s </math>

	Note that the '''interaction strength is proportional to the fourth power of the atomic number Z'''. <br>		Note that the '''interaction strength is proportional to the fourth power of the atomic number Z'''. <br>
	Doubling the atomic number causes a 16-fold increase in interaction strength. <br>		Doubling the atomic number causes a 16-fold increase in interaction strength. <br>
	So '''the Elements of the 3rd row and higher are good "drains" for getting rid of unwanted angular momentum'''. <br>		So '''the Elements of the 3rd row and higher are good "drains" for getting rid of unwanted angular momentum'''. <br>
	This is called the '''"heavy atom effect"'''. <br>		* This is called the '''"heavy atom effect"'''. <br>
	It even works if there is no direct covalent bond '''"external heavy atom effect"'''		* It even works if there is no direct covalent bond '''"external heavy atom effect"''' <br>
			How does the latter one work? There needs to be some overlap of electron wave functions right? <br>
			<small>A highly electronically isolating connection (like plain diamond can be, or a nonbonding VdW contact can be, or a minimal vacuum gap can be) is probably a bad idea right?</small>

	== Side-notes to spinning flips via ISC ==		== Side-notes to spinning flips via ISC ==

Apm: /* Why spins are "frobidden" to flip without relativistic quantum mechanics */ added subheadline

2021-07-01T08:49:37Z

Why spins are "frobidden" to flip without relativistic quantum mechanics: added subheadline

← Older revision		Revision as of 10:49, 1 July 2021
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	So there's a problem with the "willingness" part. <br>		So there's a problem with the "willingness" part. <br>
	This is just to first approximation though.		This is just to first approximation though.

			=== Relativistic quantum mechanics saving the day ===

	Taking into account effects of relativistic quantum mechanics, <br>		Taking into account effects of relativistic quantum mechanics, <br>

Apm: /* Why spins are "frobidden" to flip without relativistic quantum mechanics */

2021-07-01T08:47:45Z

Why spins are "frobidden" to flip without relativistic quantum mechanics

← Older revision		Revision as of 10:47, 1 July 2021
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	Unfortunately paired spins (singlet-state wave function) and unpaired spins (triplet-state wave function) are orthogonal wave functions <br>		Unfortunately paired spins (singlet-state wave function) and unpaired spins (triplet-state wave function) are orthogonal wave functions <br>
	meaning their overlap integral is zero – meaning they don't interact – meaning the transition is "forbidden". <br>		meaning their [[overlap integral]] is zero – meaning they don't interact – meaning the transition is "forbidden". <br>
	<small>(Meaning Fermis golden rule predict infinitely long transition time?)</small> <br>		<small>(Meaning Fermis golden rule predict infinitely long transition time?)</small> <br>
	So there's a problem with the "willingness" part. <br>		So there's a problem with the "willingness" part. <br>

Apm at 08:41, 1 July 2021

2021-07-01T08:41:16Z

← Older revision		Revision as of 10:41, 1 July 2021
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	This is due to the pauli-principle not allowint two electrons with the same spin sitting in the same (lowest energy state) orbital.		This is due to the pauli-principle not allowint two electrons with the same spin sitting in the same (lowest energy state) orbital.

			'''Spin-flipping less critical for heavier atoms like transition metals:''' <br>
	This is especially the case with light elements like carbon where filled high-energy antibinding orbitals often make a bond impossible. <br>		This is especially the case with light elements like carbon where filled high-energy antibinding orbitals often make a bond impossible. <br>
	Transition metals can from bonds with electrons in antibinding orbitals (albeit weaker bonds) and these eventually ~~deexcite~~ to become bonds of full strength. <br>		Transition metals can from bonds with electrons in antibinding orbitals (albeit weaker bonds) and these eventually de-excite to become bonds of full strength. <br>
	Still this is not desirable since this is a high energy dissipation mechanism. Devaluating a lot of un-bond Helmholtz free energy.		Still this is not at all desirable since this is a high energy dissipation mechanism. Devaluating a lot of un-bond Helmholtz free energy.

	== Flipping a spin means flipping (preserverd) angular momentum => drain needed ==		== Flipping a spin means flipping (preserverd) angular momentum => drain needed ==

Apm: removed stub marker & moved table of contents to the bottom

2021-07-01T08:38:13Z

removed stub marker & moved table of contents to the bottom

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 = Why the need for "inter system crossing" and what it is =
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 '' (Wikipedia: [http://en.wikipedia.org/wiki/Intersystem_crossing| Intersystem crossing]) <br>
 * Source of info in the intro: Video: [https://www.youtube.com/watch?v=rHbxqduwc_E]

Apm: added extensive intro

2021-07-01T08:36:54Z

added extensive intro

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 {{stub}}
 = Inter system crossing in (piezochemical) mechanosynthesis =
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 * k_isc>10^9 with ΔV_s,t >145zJ and thus
 * t_trans<10^-7s with P_err<10^-15
 = [[Nanosystems]] references =
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 '' (Wikipedia: [http://en.wikipedia.org/wiki/Intersystem_crossing| Intersystem crossing]) <br>