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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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Shortcut method to find atomic term symbols ignoring the spin orbit coupling

Is there any shortcut method by which we can find the atomic term symbols ignoring the spin-orbit coupling, i.e. ignoring the values of J. For instance, when writing the d-d transitions for any ...
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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 ...
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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 ...
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Maximum metal-metal distance for antiferromagnetic coupling

Imagine a transition metal complex with multiple open-shell transition metal cations. If the metals are relatively close in distance, it is possible that antiferromagnetic coupling will occur between ...
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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 $\...
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How to interpret a singlet term symbol for an s¹p¹ configuration?

I am interested in the $^1P_0$ singlet state of $\ce{Hg}$ ($\ce{5d^10 6s^1 6p^1}$). I interpret this to be the two following electron configurations below, because for an $S = 0$ state the two ...
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Help understanding the equation for Spin Energy in Zero Field

I’m working with a system that experiences spin frustration and for me this is the first time dealing with such a phenomenon. To grasp the concept, I’ve decided to go to the basics and read the ...
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Determining absorption spectrum, magnitude of Δo and spin for Iron Oxalate

Iron Oxalate ions form an emerald green solution when dissolved. If the ions in solution appears emerald green to our eyes, what color of visible light is it mostly absorbing? What does that tell you ...
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Distinguish between two possible configurations for angular momentum in carbon atom

Consider the possible values of $S$ and $L$ for carbon configuration $1s^2 2s^2 2p^2$ and the corresponding rapresentations with arrows indicating the spins (consider only $S=0,L=0$ and $S=0,L=2$, as ...
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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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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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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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Help understanding external magnetic field sensitivity of radical pair reaction rate

Two recent papers have been published on magnetoreception in birds. In this case it is the ability of the birds to sense the direction of the Earth's magnetic field potentially for navigation. ...
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Total spin number 0 together with $B_2$ state - confusion

I'm trying to understand molecular symmetry and I got confused reading the Molpro documentation. There is an example of a system with $B_2$ symmetry written like this: $$ wf,10,3,0, $$ which means, ...
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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 ...
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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 ...
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Which electron is knocked off a Helium atom?

When a He atom is ionized, which electron is removed first, the one with the spin up or down? or is it just random?
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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 ...
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Are electrons in a helium atom diametrically opposite? [closed]

The helium atom is represented with electron opposite on same orbital: not fully opposite on same orbital and even on two normal orbitals: But in this case wouldn't the electron crash? Can you ...
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A question on spin of an electron [closed]

Can an electron have zero spin? In para hydrogen, since the nuclei have opposite spins, the they add up to 0. So is it true that one electron can have zero spin?
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Do the spins of outer orbitals block measurement of spin of inner orbitals?

Do the outermost s1 and s2 electrons block an outside observer from measuring the larger inner group orbitals for elements heavier than Nitrogen (for instance, would Chromium's 4s1 electron or ...
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Potential energy surface when spin changes

I'm trying to compute potential energy surface of S4 molecule (in MOLPRO 2015) along S2-S2 bond (it has a trapezoidal shape) from equilibrium to the dissociation threshold, all the other coordinates ...
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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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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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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?...
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Band structure in half-metals

In a typical band diagram of a half-metal, the band structures for electrons of up and down spin are different. Why is this so?
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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 ...
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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 ...
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Rotational Constant for CO2 from an IR Vibrational-Rotational spectra

I have been trying to calculate the rotational constants ($B$) for $\ce{CO}$ and $\ce{CO2}$ from IR Vibrational-Rotational spectra. I know that for $\ce{CO}$ the peak spacing is approximately $2B$ (...
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Nomenclature of This State?

I've read this in a book It says the state having three parallel spin is called triplet state . But as far as I know it is determined by "2S+1", from this it comes out to be 4 . Then how it is "...
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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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Is Nuclear Spin Isomer a kind of allotrope?

In my book there's a question: Does $\ce{H2}$ shows allotropy ? Enlist its allotropes and their application? I pondered over different way Hydrogen can be arranged(I don't know but I have weak ...
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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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How fast do electron's quantum spin flip?

In a recent lecture it was taught that carbenes with their electrons in a triplet configuration do not undergo concerted reactions as one of the electrons must first undergo a spin flip; on what ...
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Electron has volume or not?

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 ...
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Can fluorescent & phosphorescent molecules still be fluorescent or phosphorescent as ions and not as salts?

The way my pchem professor explained it is that fluorescence /phosphorescence is caused by collision excitation. During this collision the spin of the promoted electron is flipped to a parallel spin ...
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Stability of ortho and para hydrogen [duplicate]

I have two books on inorganic chemistry, one says that ortho hydrogen is more stable while other says para is more stable. Even on Internet, there are websites some supporting the former fact and some ...
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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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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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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 ...
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227 views

Nuclear spin isomerism in molecules other than H2

I was reading my teacher's material about ortho- and para- hydrogen, and I found stated that "every homonuclear molecule, with nuclides with spin other than zero ($\ce{H2}$, $\ce{D2}$, $\ce{T2}$, $...
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Derivation of the form of the time correlation function in NMR spectroscopy

For a given protein, I know that the NMR spectrometer magnet generates a field $B_0$ and that the interactions with the spins in the local environment generates a much smaller field $B_\mathrm{loc}$ (...
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Transition from ground state to excited state

I don't understand how to correctly find the term symbol of an excited state. I know that the first two permitted transitions for the Ne atom are 16.8eV and 19.8eV and I want to find the electronic ...
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Is the reasoning of spin contamination correct?

The common explanation of spin contamination is like the following: The non-relativistic electronic Hamiltonian commutes with $S^2$ and $S_z$. Hence, the exact eigenfunction should be an ...
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560 views

2 electrons with the same spin in the same orbital

When two electrons are in the same orbital and they have the same spin do we say that the electronic configuration is impossible or that it refers to an excited state?
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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 ...
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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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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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Filling up of electrons [duplicate]

Is it necessary that filling up orbitals start from spin-up orientation only? And also, is it mandatory to fill the electrons with one kind of spin or they can be filled with spin up and spin down(as ...
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807 views

Change in spin angular momentum during transition in one-electron atoms

I have a really basic qustion about spin and electronic transitions. In one-electron systems (like H or $\ce{He+}$), will the electron change its spin during an electronic transition? Let's say the ...