What is Spin: Definition and 1000 Discussions

Trying to get my head around this one. Given that you can have a proton and an electron in a hydrogen atom for example, and they can create a singlet or triplet configuration, with spin 1 and spin 0 respectively. The total spin operator can be derived as: S^2 = (Se + Sp)^2 = Se^2 + Sp^2 +...

Homework Statement The interaction between the spins of the two particles in a hydrogenic atom can be described by the interaction Hamiltonian $$\hat{H_I} = A \hat{S_1} \cdot \hat{S_2}.$$ Compute the splitting of the ground state due to ##\hat{H_I}##. Both particles have spin 1/2. Homework...

Number of Spin "s" States Homework Statement For a system of two identical particles with spin s, determine the number of symmetric and anti-symmetric spin states. 2. The attempt at a solution This does not seem like a problem that is that difficult, but I am having some trouble...

Hello Everyone, General curiosity question. We start with a particle who is in superposition. We observe it and collapse its wave function. This is how the particle's spin is determined. Two states can exist, spin up or spin down. My question is, once we observe the spin state, is...

A spin 1/2 particle A undergoes decay A→B+C+D Where it is known that B and C are also spin 1/2. The complete set of allowed values of spin of D It was a Multiple Choice Question and options given were 1) 1/2,1,3/2,2,5/2,3,... 2) 0,1 3) 1/2 only 4) 1/2,3/2,5/2,7/2,... I tried the...

Spin Foam Gravity (SFG) has reached a stage of development where perhaps we could have a new abbreviation to distinguish it from previous Loop gravity formulations. I could be wrong about this, of course, but I want to see how things look from that angle. There seem to be some...

Homework Statement Homework Equations The Attempt at a Solution Angular momentum is the only parameter conserved. This is because there are no external torques acting on the system. Energy is not conserved because the collision is inelastic. Finally, linear momentum is not...

Spin is an operator with components (Sx,Sy,Sz) but do these represent "spatial" components. The question arose because the spin of an electron sets up an angular momentum L = -e/m * S (S and L are vectors) So inverting the spatial coordinate system and requiring that the physical result must...

Hi, I have a few questions regarding the experimental outcome of the stern-gerlach experiment. Let's suppose the following setup: We have a magnetic field whose field-lines point towards the positive z axis and the intensity of that field becomes stronger towards the positive z axis, so there...

I am currently confused... I read that we don't know yet where does the proton spin come from. But I wonder... 1) Doesn't the proton have effectively 3 quarks of spin 1/2 (I said effectively to leave out the quark-gluon sea within the proton)? In that case, 3 spin 1/2 particles can't be added...

The 3s and 3p orbitals are filled by 4 electrons.A single atom has [Ne]3s2 3p2.But when multiple atoms get together they do so in order to minimize the overall energy.And to minimize the overall energy,the 3s and 3p orbitals hybridize to form 4 tetrahedral SP3 orbitals.And the Si atoms get...

We say that spin is an intrinsic angular momentum which does not have anything to do with space. But is it possible that it is the orbital angular momentum of some internal constituent particles (a yet unknown fine structure)?

Homework Statement Consider a system of two spin 1/2 particles, labeled 1 and 2. The Pauli spin matrices associated with each particle may then be written as \vec{\hat{\sigma _{1}}} , \vec{\hat{\sigma _{2}}} a)Prove that the operator \hat{A]}\equiv \vec{\hat{\sigma _{1}}}\cdot...

When a electron or any charge spins what is the direction of the magnetic field generated by its spin? what is the rule connecting the direction of spin of the charge and direction of magnetic field

does nucleus in an atom spin?

I thought this was cool, wasn't able to find a paper on it, but didn't look "super hard", and won't pay for it. Apparently, a gravitational lensing has lined up so perfectly that we were able to measure the black hole's spin. They have it at "half the speed of light" (??!)...

hello guys , in this problem from zettili quantum mechanics that i attach , i think something is wrong , first the problem said two particles with spin 1/2 but didn't mention that the system is in singlet state or triplet state , so if the system be in triplet state then our spatial wave...

Spin-1 matrix Sx, Sy, Sz are traceless 3*3 matrix, and have the property ##[S_i, S_j] = i\epsilon_{ijk}S_k##, and we know that ##Tr(S_i^2) = 1^2+0^2+(-1)^2=2##. All of the above are independent of representation, of course, the trace of a matrix is representation-independent. so, if we want...

Homework Statement For a spin 1/2 system, the eigenstates of z-component of the angular-momentum operator Sz are given by: S_z |\pm> = \pm \frac{\hbar}{2}|\pm> Suppose at time t, the state of the system is given by: |\psi> = a|+> + b|-> If Sz is measured, what are the possible results of...

Question about quantum spin: So for the Schrodinger equation, the angular momentum of a wave-packet, whether it is free or confined to a potential well, appears to be calculated in exactly the manner you would expect it to be: L(x) = m*rxv[Psi(x)]. Aside from quantization (decomposing the...

Hi everybody, In most classical or quantum optics texts an angular momentum is considered for the EM radiation as the following: J = ε_0 ∫_V r × [E(r, t) × B(r, t)] d^3 r Then it is claimed that: "Using the usual formula for a double vector product and integrating by parts...

Hi, this probably has been answered somewhere here already, but I was unable to find it. Could someone explain how the spin of a particle is actually measured in an experiment ? Most interesting to me is how the 3d spin vector for 1/2 spin particles is determined experimentally. Cheers.

The spin angular momentum of a spin 1/2 particle is given by S = √(s(s+1))ℏ. If s =1/2, S= ((√3)/2)ℏ So, if s=1 is S= √2ℏ ?

The epr paradox is usually explained as something like: Suppose you have two electrons in the singlet state (+=spin up, -=spin down): lψ>= l+>l-> - l->l+> Now if you measure the spin on the first electron the explanation is (I think) that this collapses one electron onto l+> or l-> such...

Hi PF members. I have got a little worry I am familiar with the Zeeman term that always appears in the Hamiltonian of a spin chain representing the influence of an external magnetic field. I don't know if there is a similar term if the spin was rather in he presence of an electric field ( I...

I am reading a text about the splitting of the energy levels in crystals caused by the spin orbit interaction. In particular, the argument is treated from the point of view of the group theory. The text starts saying that a representation (TxD) for the double group can be obtained from the...

Homework Statement An alkali atom, on it's fundamental state, passes through a Stern-Gerlach apparatum, which will only transmit atoms with their spins aligned along the +z direction. After that the atoms travel, during a finite time τ, through a region of constant magnetic field...

So I know this might be a lot to read but I am having a very hard time understanding how to use the formulas in degenerate perturbation theory. Here is the problem I am on. Homework Statement A system of two spin-1/2 particles is described by the following Hamiltonian...

quantum spin vs ...spin I keep hearing people say, "comparing particle spin to a spinning top will lead you in the wrong direction." I'm curious.. what exactly is the difference between the two?

What is the link between the polarisation of light and photon spin?

In my textbook there is an equation for the precession frequency: Ω = τ/Iω The derivation in the book shows no difference in the spin angular momentum at time t = 0 and t = delta t but when I tried it I got that the denominator of the above equation must be the 'new' angular momentum (at t...

Hi, please could someone provide me with an explanation of the differences between the magnetic quantum number and the spin. I thought that the magnetism of an electron/fermion comes from its intrinsic quantum angular momentum (i.e. its quantum spin) which was evidenced by the Stern–Gerlach...

Homework Statement Consider an electron with spin \frac{1}{2} and orbital angular momentum l=1. Write down all possible total angular momentum states as a combination of the product states | l=1 , m_l > | s = \frac{1}{2} , m_s > Homework Equations Lowering operator : J_- |j, m> =...

Hi, please could someone explain the notion that particles of 1/2 integer spin do not look the same when turned through 360 degrees. This notion seems to crop up when I read around QM but nobody seems to explain how this came about. So my question is this - what experiment shows/confirms that...

Suppose we consider the spin 1/2 measurement matrices B=\frac{1}{\sqrt{2}}\left(\begin{array}{cc} 1 & 1\\1&-1\end{array}\right) and A=diag(1,-1) it's easy to show that B^2=A and a normalized eigenstate of B |\Psi\rangle=\left(\begin{array}{c}a\\b\end{array}\right) with eigenvalue 1 ...

What is the Lagrangian of interaction of photon and spin zero charge scalar?The vertex of photon and spin 1/2 charge fermion is proportional with e multiplied vertor gamma matrix,but I do not know what is the vertex of photon and charge scalar.I hear that a vertex is proportional with polynomial...

Dear members, I'd like to collect those properties of "spin" that makes it different to a normal (classical) angular momentum or magnetic moment. Please help me, correct, reword my sentences one by one. I'd like to create a short but still understandable and correct list. 1. Spin quantum...

how actually electron and protons spin? explain me whether this spinning could provide torque to the positive charges then it means electrons and protons keeps rotating under their electrostatic field?

i am actually calculating the nuclear spin of Sodium 23. Here we have 11 protons and 12 neutrons. Now both the nuclei are short of the magic numbers. When I use the shell model for protons and neutrons separately, I found 3 protons in the 1d5/2 sub-shell and 4 neutrons in the same 1d5/2...

Recently, I was thinking about spin and isospin. It's been a while since I've dealt with particle physics, so my knowledge may be a bit rusty. In the Standard Model, we have three interactions with associated coupling constants e, gw and gs. A particle may have three different charges Qe, Qw...

Homework Statement Two particles with spin 1/2 and are in the spin state: |\psi> = |\uparrow_{1}>|\downarrow_{2}> where |\uparrow_{1}> is a state where particle 1 has spin up along the z-axis and |\downarrow_{2}> is a state where particle 2 is spin down along the z-axis. If...

Sorry if it is a silly question: Photons have spin-1 and therefore they have theoretically three possible spin states (1,0,-1), For the ±1 case I can see the relation to the ±helicity, but what corresponds physically to the 0 state case?

Homework Statement https://fbcdn-sphotos-c-a.akamaihd.net/hphotos-ak-prn2/1483071_10151813160569290_1331827985_n.jpg Homework Equations \left|\psi ,t\right\rangle=\sum_i c_i(t)e^{-\frac{i E_n t}{\hbar}}\left|n\right\rangle The Attempt at a Solution I'm quite lost on how to even start this...

hi all, i am interested in MRI, and i wish to know what is the scientific theory telling us that the spins will precess in phase if they were placed in an external field and exposed to a 90° RF pulse. what i know is that the nuclei will precess at the same angular frequency (or same angular...

Homework Statement I'd like to calculate the probability of a spin flip transition occurring in the ground state of neutral hydrogen. That is, the transition from parallel to anti-parallel spin configuration of the electron and proton. This transition produces the 21-cm line. Homework...

Homework Statement If a particle has spin 1/2 and is in a state with orbital angular momentum L, there are two basis states with total z-component of angular momentum m*hbar l L,s,Lz,sz > which can be expressed in terms of the individual states ( l L,s,Lz,sz > = l L,Lz > l s,sz > ) as l...

In my lecture notes, there is a slide about an external field interacting with a system of electron spins. In this situation can we assume that B=B_0 ( or in other words that μ_0*M =0)? I would think so, but does a system of electron spins imply that these electrons belong to some matter...

Homework Statement What are the possible results of the measurement of the sum of the x and z components of the spin angular momentum of a spin-1/2 particle? Sx = Spin angular momentum operator x Sz = Spin angular momentum operator x Homework Equations The Attempt at a...

can we spin a shpere of air? not the shell only, but the whole volume itself spinning on it's axis, can we do that and let a ball of air spin with momentum, and if it is fast enough, it would form such a centrifugal force that it can maintain itself without keeping on spinning it

It's frequently mentioned in introductory quantum mechanics texts that Goudsmit and Uhlenbeck conjectured that the magnetic moment of an electron was due to angular momentum arising from the electron rotating around its own axis. But then when they tried to calculate how fast it would have to...