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Questions tagged [spin]

Spin is a type of angular momentum which is intrinsic to atomic and sub-atomic particles. Electrons in orbitals can be either spin paired or spin unpaired which influences the magnetic properties of the species containing these orbitals.

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What is the physical basis for Hund's first rule?

According to Hund's first rule, a set of degenerate orbitals are singly occupied first, before the second slot in any of the orbitals are populated. This is quite intuitive because electron-electron ...
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What is antisymmetric exchange? What is J-strain? Where does it come from?

I'm reading a paper1 by Sanakis, et al. that characterises the magnetic coupling in the $\ce{Fe3S4}$ clusters present in bacterial ferredoxin II and beef heart aconitase as arising through something ...
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21 votes
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What happens when para-water ice is suddenly melted?

Background (hydrogen) In the case of recently liquified hydrogen (which is quite cold of course) it must be re-equilibrated before loading on to a rocket as fuel to avoid a sudden exothermic ...
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Do Electrons Really 'Spin'?

With regard to the 'Electron Spin Number', lots of websites mention that electrons don't really spin and that the electron spin number has nothing to do with any physical spinning. However, my ...
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How to convert from spin orbitals to spatial orbitals in the Hartree-Fock approximation?

I need to calculate some of the more complicated self-energy terms from chapter 7 of Szabo and Ostlund's "Modern Quantum Chemistry", and I'm having trouble converting summations from spin orbitals to ...
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Are there any examples of nuclear spin isomers having consequences for chemical reactivity?

Ortho- and parahydrogen are two forms of the $\ce{H2}$ molecule that are distinguished by their pairing or antipairing of nuclear spins, giving rise to metastable singlet (ortho-) and triplet (para-) ...
Richard Terrett's user avatar
11 votes
1 answer
288 views

Grasping the concept of Electronic Spin, Effective Spin and Fictitious Spin

Trying to learn alone some aspects of quantum mechanics is, sometimes, a struggle. Reading the excellent paper by Piwowarska [1] I was hoping to, finally, understand what is the origin of the so-...
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Do electrons only fill 'spin up' first? Or could it start filling 'down spins' first? [duplicate]

Due to Hund's rule, electrons start filling up the orbitals without pairing up. When this is happening, do the electrons all fill up the 'up' spin? Could they fill in the 'down' spin? Why do they ...
IlIIlllIIIlIIlllIlIllIIIlIlI's user avatar
11 votes
1 answer
391 views

How to derive Pauli Exclusion Principle without assuming anti-symmetry?

So, it appears that the statement of the Pauli Exclusion Principle is equivalent to the statement that fermions are anti-symmetric. That is, if you assume that fermions are anti-symmetric, then you ...
T. Zack Crawford's user avatar
10 votes
2 answers
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What does an electron's spin of 0.5 and minus 0.5 signify?

While teaching me magnetism, my teacher told me about the spin of an electron. He told me that the spin of .5 means that if we rotate the electron twice counter-clockwise on its axis, we would have ...
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Name for a spin state with a multiplicity of 13

If I want to name a spin state with 12 unpaired electrons, what is the correct name? Tredecim is the latin name for thirteen, but tredecimet sounds odd.
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Can an organic molecule have a triplet ground state?

Can the ground state of an organic molecule be a triplet. This would imply something like a "HOMO" formed by 2 degenerate levels and less than 4 electrons to fill them. If yes, what are the conditions?...
matteo's user avatar
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3 answers
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Atoms or molecules with spin 1 in the ground state?

Is there any atom or molecule that has spin 1 in its ground state? Do Hund's rules keep this from happening for an atom? The reason I'm curious is that it would be nice to have a spin-1 example for ...
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8 votes
4 answers
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Is the order of orientation of electron box diagrams meaningful or arbitrary?

Here is my interpretation when asked to: By drawing arrows in the appropriate boxes, complete the outer electron structures for Cu and Cu2+ I had no problem in drawing out the electron structure, ...
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Why do spin isomers of hydrogen (ortho and para hydrogen) change their nuclear spin with temperature variance?

My book says that ordinary dihydrogen contains 75% ortho and 25% para forms of hydrogen, while at significantly lower temperatures (like 20K) ortho and para hydrogens are 0.18% and 99.82% respectively....
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Total magnetic moment of atom

Whenever I read about coordination compounds in my textbooks, I always find a discussion about spin-only magnetic moment which is given by $\sqrt{n(n+2)}\cdot\mu_\mathrm{B}$, where $n$ is the number ...
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Only d orbital electrons for spin only magnetic moment

During my chemistry lessons and self studies, I have come upon many instances where I observed that during calculations of spin only magnetic moment of transition elements only the d orbital electrons ...
glucose's user avatar
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"Hamiltonian operator has no effect on the spin function" what does it mean?

I have read the Levine Quantum Chemistry book and it says "Hamiltonian operator has no effect on the spin function" in chapter 10 (Electron Spin and the Spin-Statistics Theorem) and does the ...
Subhadip Pal's user avatar
7 votes
1 answer
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Confusion about the number of microstates for orbitals

I am very confused about the microstates for a specific orbital. Let's suppose I have an electronic configuration $$ \ce{[\dots] 2p^5} $$ Considering the symmetry of the orbitals and the "...
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NMR - coupling of chemically equivalent protons

In Klein's Organic Chemistry 3rd Edition page 671, it states This observation, called the n + 1 rule, only applies when all of the neighboring protons are chemically equivalent to each other. ...
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Electron has volume or not? [duplicate]

Sometimes we say that electron has volume, as in orbital we can define it's volume (at least for some fraction, as orbital itself has no limit, it is spread all over the space expect nodes). On other ...
Aditya Shrivastava's user avatar
6 votes
1 answer
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Mechanism for interconversion of spin isomers of hydrogen

What is the mechanism by which the ortho- and para- spin isomers of hydrogen interconvert? If such a mechanism exists, does this mean that ortho-hydrogen increases in concentration on increasing ...
Shivay Vadhera's user avatar
6 votes
1 answer
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Is [Co(NH₃)₄Cl₂]Cl paramagnetic or diamagnetic?

$\ce{NH3}$ is known to be a strong field ligand, while $\ce{Cl}$ is known to be a weak field ligand. Is $\ce{[Co(NH3)4Cl2]Cl}$ a high spin complex or a low spin complex? I assumed this to be a high ...
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Mulliken Spin Density

I would like to know if a Mulliken population analysis to calculate spin densities is in general a valid choice. I see that it is made use of, for example here1. So up to-date researches apparently ...
Martin 's user avatar
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How long would it take for a tank of same-spin hydrogen atoms to become a tank of H₂?

In the question Is there an energy cost associated with flipping the spin of an electron?, it is shown that it is very unlikely for two hydrogen atoms to bond if their electrons have the same spin. ...
Display Name's user avatar
6 votes
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"Alternative" derivation of the spin-only formula

The spin-only formula $$\mu_\mathrm{so} = \mu_\mathrm{B} \sqrt{n(n+2)} = \mu_\mathrm{B}\cdot 2\sqrt{S(S+1)}$$ is usually a good first approximation to calculate the magnetic moment of transition ...
orthocresol's user avatar
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5 votes
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366 views

Are nuclear spin isomers "allotropes"?

In my book there's a question: Does $\ce{H2}$ show allotropy ? Describe its allotropes and their applications. Wikipedia doesn't list any allotropes of $\ce{H2}$. However, when searching on the ...
Xasel's user avatar
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1 answer
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Can an electron be excited to a spin state with s ≠ 1/2?

I used to think that all nuclei have fixed intrinsic value of the nuclear spin quantum number, $I$. For example, $\ce{^1H}$ must have a nuclear spin of $\frac{1}{2}$, $\ce{^{14}N}$ must have a nuclear ...
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Carbon-13 NMR for chloroform

I am slightly confused by what the spectrum would show for carbon-13 NMR of $\ce{CHCl3}$. My initial guess would be that the peak would be split by coupling to both the proton and the 3 chlorines, as ...
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5 votes
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Why only one peak is observed in NMR spectrum of H2?

Assuming a downward magnetic field is applied and the nuclear spin of two equivalent protons in $\ce{H2}$ are all in ground state $\downarrow\downarrow$ initially. Would the required energy of one of ...
Junbo's user avatar
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5 votes
1 answer
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How to derive the nuclear spin of 23Na?

Is it possible to derive the nuclear spin I=3/2 for $\ce{^23Na}$ from a term scheme or from something else from spectroscopy? I thought the nucleus spin is empirical (and cannot be calculated from J ...
laminin's user avatar
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5 votes
1 answer
355 views

How is a NMR spectrum obtained?

I am reading about NMR, and from what I'm understanding it should give information on the transition energies in the spectrum of the nuclear spin in a magnetic field. What I don't understand is how ...
tbt's user avatar
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1 answer
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Can geometry of a molecule change when the spin-orbit coupling is taken into account? [closed]

Cross-posted on MMSE. Is there any evidence that spin-orbit coupling (SOC) leads to significant changes in atomic structure? Using DFT, I am getting different relaxed lattice constants when I take SOC ...
freude's user avatar
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5 votes
0 answers
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What is the magnetic moment of potassium hexacyanochromate(II)?

I calculated the magnetic moment of $\ce{K4[Cr(CN)6]}$? in the following way: $\ce{Cr^{+2}}$ has $4$ d electrons. And since $\ce{CN-}$ is a strong field ligand, the electrons will pair up in the $\...
SmarthBansal's user avatar
5 votes
0 answers
316 views

Why is spin-contamination undesirable?

Why is spin-contamination, introduced by e.g. Unrestricted Hartree Fock, undesirable, and to which problems further on can it lead? The only problem I currently see myself is that spin-contamined ...
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Why does diamagnetic current induce a downfield while the paramagnetic current induces an upfield shift?

I know that aromatic rings exhibit diamagnetic ring currents which causes the protons outside the ring to go downfield in H-NMR. Antiaromatic compounds exhibit paramagnetic ring currents which have ...
EJC's user avatar
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4 votes
1 answer
713 views

Difference between spin-orbit coupling and the Russell-Saunders Effect?

The Russell-Saunders effect is the same thing as 'spin-orbit interaction, correct? The reason I am asking is because I was reviewing the Wikipedia page on 'spin-orbit interaction' and it does not ...
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4 votes
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Does an electron's spin change when being excited?

My preconception is that when you fill an empty orbital by exciting an electron (with a photon), the empty orbital should be filled by an electron with the same spin. However, I've seen examples of ...
biryaniboi's user avatar
4 votes
2 answers
8k views

What accounts for the high spin state of the complex Tris(acetylacetonato)iron(III)?

I understand that there's 5 d-electrons for $\ce{Fe^3+}$ ion, but why it doesn't fill up the lower energy orbitals first to form one unpaired electron, but rather, filling up all the orbitals to form ...
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4 votes
1 answer
419 views

Spin interaction term for a two-particle system of fermions with a potential that contains spin-spin interaction

Consider a two-particle system consisting of two identical fermions in a potential $$V(\vec{r})\vec{\sigma_{1}}\cdot\vec{\sigma_{2}}$$ where $V(\vec{r})$ is the spatial part of the potential and the ...
TheQuantumMan's user avatar
4 votes
1 answer
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Term Symbol for Carbon

Currently studying how to "compute" term symbols. My book gives the example of carbon. Carbon has the electron configuration $(1s)^2(2s)^2(2p)^2$. We can ignore full orbitals, so we only ...
xotix's user avatar
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4 votes
1 answer
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How to calculate S² value of a broken-symmetry wave function?

$S$ represents spin, signifies the number of unpaired electrons in the system. For example, if the number of unpaired electrons is $1$, then $S=1/2$. $S^2$ is calculated as $S(S+1)$. From what I have ...
tobiuchiha's user avatar
4 votes
1 answer
313 views

Determining spin of metal complex

Is there any way to determine the spin of $\ce{[Fe(OH)6]^{4-}}$ without looking at the spectrochemical series?
dogman288's user avatar
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0 answers
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How to calculate the spin of atomic nuclei?

I have recently been learning about nuclear magnetic resonance spectroscopy. It is mentioned that the spin of the $^{1}$H nucleus is $\frac{1}{2}\ $and the spin of the $^{2}$H nucleus is $1$. This ...
Tan Yong Boon's user avatar
3 votes
1 answer
236 views

Why are most organic molecules diamagnetic, when most of them have non-paired nucleus spins?

I was studying some coordination chemistry and somewhere around the text it was stated that one could know the magnetic moment of a complex from its metal because since all ligands were often ...
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3 votes
2 answers
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NMR: How the relaxation times T1 and T2 depend on the correlation time / amount of molecular tumbling.

Why do nuclei that have a smaller / faster correlation time have a higher / slower T1 / T2? From my understanding: Fast Brownian motion creates a wide range of B.local (local magnetic field created ...
Noah Harrison's user avatar
3 votes
1 answer
996 views

Spin spin coupling in a proton NMR of an ester?

I am learning about proton NMR and spin-spin coupling, and am confused about whether splitting occurs over an ester bond. Specifically, in the case of ethyl methanoate, HCOOCH2CH3, if I were to number ...
Meep's user avatar
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3 votes
1 answer
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Why is a spin change favourable in intersystem crossing?

All phosphorescent molecules go through the following transitions: $$\text{excited singlet state}$$ $$\Bigg\downarrow$$ $$\text{[intersystem crossing]}$$ $$\Bigg\downarrow$$ $$\text{ excited triplet ...
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1 answer
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How can Spin-Orbit-Coupling allow interactions between states with different multiplicities?

I can understand how spin-orbit coupling generates the hyperfine structures that we see in textbooks but maybe my view that the L + S momenta interacting to generate a third J momentum is too ...
HCSthe2nd's user avatar
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3 votes
2 answers
258 views

Methylene "anti" Jahn-Teller effect

Yesterday a Reddit user posted a page from Morrison's Organic Chemistry in which it is said that singlet methylene is less stable than triplet methylene. Another user asked basically the same I'm ...
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