- #1
Lebnm
- 31
- 1
Thread moved from a technical forum, hence missing template
Can someone help me with this excercise?: Consider two electrons constrained to move in one dimension. They interact through the potential
$$
V(x) = \begin{cases}
0, & \text{ if } |x| > a \\
-V_{0}, & \text{ if } |x| \leq a
\end{cases}
$$
where ##x## is the relative coordinate. The total spin is ##S = 1##, and the objective is to determine the state of the system.
I know I can write the state as ##|\Psi \rangle = |P \rangle \otimes |\psi \rangle \otimes |SM \rangle##, where ##|P \rangle## is an eigenstate of the momentum of CM, and the wave function ##\psi (x) = \langle x | \psi \rangle ## is the solution of $$-\frac{\hbar^{2}}{2\mu}\frac{\mathrm{d^{2}}\psi }{\mathrm{d} x^{2}} + V(x)\psi(x) = E \psi(x).$$ Now, I know that the states ##|P \rangle## and ##|SM \rangle ## with ##S=1## are symmetric over permutation of the electrons, but I don't know how to determine if ##|\psi \rangle## is either symmetric or antisymmetric. In this case, the permutation of the electrons change ##x \rightarrow -x##, so it has the same effect of parity. The hamiltnian above is obviously invariant over parity, and there is a theorem that says ##|\psi \rangle## is an eigenstate of parity (suposing that the spectrum of the hamiltonian is non-degenerated), so it have to be symmetic or antisymmetic. Do I need to determine the wave function ##\psi(x)## to it? I tried to do this, but I get four constants that I can't determine.
$$
V(x) = \begin{cases}
0, & \text{ if } |x| > a \\
-V_{0}, & \text{ if } |x| \leq a
\end{cases}
$$
where ##x## is the relative coordinate. The total spin is ##S = 1##, and the objective is to determine the state of the system.
I know I can write the state as ##|\Psi \rangle = |P \rangle \otimes |\psi \rangle \otimes |SM \rangle##, where ##|P \rangle## is an eigenstate of the momentum of CM, and the wave function ##\psi (x) = \langle x | \psi \rangle ## is the solution of $$-\frac{\hbar^{2}}{2\mu}\frac{\mathrm{d^{2}}\psi }{\mathrm{d} x^{2}} + V(x)\psi(x) = E \psi(x).$$ Now, I know that the states ##|P \rangle## and ##|SM \rangle ## with ##S=1## are symmetric over permutation of the electrons, but I don't know how to determine if ##|\psi \rangle## is either symmetric or antisymmetric. In this case, the permutation of the electrons change ##x \rightarrow -x##, so it has the same effect of parity. The hamiltnian above is obviously invariant over parity, and there is a theorem that says ##|\psi \rangle## is an eigenstate of parity (suposing that the spectrum of the hamiltonian is non-degenerated), so it have to be symmetic or antisymmetic. Do I need to determine the wave function ##\psi(x)## to it? I tried to do this, but I get four constants that I can't determine.