Recent content by yxgao

  1. Y

    Two distinguishable particles space-spin wavefunctions

    Hi! Two (distinguishable) non-interacting electrons are in an infinite square well with hard walls at x=0 and x=a, so that the one particle states are \phi_n(x)=\sqrt{\frac{2}{a}} sin(\frac{n\pi}{a}x), E_n=n^2K where K=\pi^2\hbar^2/(2ma^2) My question is what are the spins and space-spin...
  2. Y

    Evaluating integral born approximation

    I made a mistake in my equation. The correct one is this: f(\theta)=\int r e^{\frac{-r^2}{a^2}} sin(kr) dr where a is a constant. This equation gives the scattering amplitude for spherical symmetry. If I write this as: f(\theta)=\int r^2 e^{\frac{-r^2}{a^2}} \frac{sin(kr)}{r} dr...
  3. Y

    Quantum mech question - hydrogen help?

    Hi, can someone help me with this problem? A hydrogen atom is in the 2P state with n=2, l=1, m=1. It emits a photon and makes a transition to the 1S state (n=1, l=0, m=0). The question is what is the probability distribution of the direction (\theta , \phi) of the emitted photon? The...
  4. Y

    Help quantum mech hydrogen molecule and spin

    Hi, I'm confused once again about a spin problem. The nuclei in a hydrogen molecule are identical protons. Spin states can be ortho (triplets) with parallel spin or para (singlets) with antiparallel spin. What are the three lowest energies for the para and ortho hydrogen molecules...
  5. Y

    Evaluating integral born approximation

    Hi, I'm trying to evaluate the following integral to calculate the scattering cross section for a spherically symmetrical potential e^{\frac{-r^2}{a^2}}? f(\theta)=\int r e^{\frac{-r^2}{a^2}} sin(kr) dr where a is a constant. What is the easiest way to evaluate this? I was able to get...
  6. Y

    Infinite solenoid with magnetic flux

    Hi, I have a question as follows. For an infinite solenoid with magnetic flux \Phi, for what values of \Phi "is the quantum mechanical motion of an electron constrained to stray far from the solenoid exactly the same as it would be if \Phi were zero"? Solution: \Phi = n \Phi_{o} with n =...
  7. Y

    Quantum mech help - radii of some atoms

    What is the ratio of the radii of muonic hydrogen to hydrogen? Muonic hydrogen consists of a proton and \mu^{-}. How do you calculate this??
  8. Y

    Baryons & addition of angular momentum

    Thanks for your detailed explanation. How do you go from the last expression in the third to last line to the second to last line? Why do you only have 7 and not 8 terms in the parenthesis? Thx
  9. Y

    Why Does a Half Harmonic Oscillator Only Allow Odd Quantum Numbers?

    Why does the half of a harmonic oscillator potential allow only odd values of n? Thx
  10. Y

    What Are the Possible Spin States After Particle Decay in Quantum Mechanics?

    Hi, I'm having problems with this quantum mechanics problem. This is from a practice final I found online somewhere. A particle of spin S has either spin S=0 or spin S=1. It decays into two electrons, and the spin of the two electrons is that of the original particle. The electrons come out...
  11. Y

    Baryons & addition of angular momentum

    That's what the solution said. I don't fully understand the theorem. Is there any way you can explain this better, in context of the problem? Thanks a lot for help!
  12. Y

    Bringing Some Humor to Laser Diodes: Fun Jokes

    Thx guys for your posts. This was the only one that made me laugh, but I had already found it online. I guess there aren't too many good ones, but the stories you posted were really funny.
  13. Y

    Baryons & addition of angular momentum

    I was wondering if someone could help me explain this problem. In a baryon, two quarks are in l=0 and one quark is in the l=1 state. Quarks are spin-1/2 particles. What values can the total angular momentum take? I know the answer is 1/2, 3/2, and 5/2, but I'm confused about how they...
  14. Y

    Bringing Some Humor to Laser Diodes: Fun Jokes

    Does anyone know any laser jokes? I'm doing a short presentation on laser diodes and thought it might be fun to include a refreshing page of jokes near the end. I found a few on Google, but none were very funny.
  15. Y

    What is the resonance frequency expression for a parallel RLC circuit?

    Thanks! I really appreciate it! \lambda \mu
Back
Top