- #1
Useong
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Hi, I am new here. I am a graduate student of department of physics at some university in Korea. If there is any wrong in my english, I will apologize in advance. I am preparing for my qualifying exam that is going to be held on next month.
The question is very simple as I stated in the title. "Can you infer the principal quantum number from a given wave function of the hydrogen atom?" Not by memorizing but by logical deduction. I think no one can memorize all of the wave functions of the hydrogen atom.
For example, you are given this wave function [tex]\psi _{nlm} = \frac{1}{{\sqrt {4\pi } }}\left( {\frac{1}{{2a}}} \right)^{3/2} \left( {2 - \frac{r}{a}} \right)e^{ - r/2a} [/tex]
where[tex]a = \frac{\hbar }{{me^2 }}[/tex]. Of cource, you may know the Hamiltonian that is composed of the kinetic term and the Coulomb potential.
[tex] H = - \frac{{\hbar ^2 }}{{2m}}\nabla ^2 - \frac{{e^2 }}{r} [/tex]
The principal quantum number of above wave equation is 2. But how would you infer it?
I tried this method. I know the energy eigenvalue is given by
[tex]E_n = - \frac{{e^2 }}{{2a}}\frac{1}{{n^2 }}[/tex]
So, when I carried out the integration to find the energy eigenvalue, I could obtain
[tex]E_n = \iiint {d^3 r\psi _{nlm}^ * \hat H\psi _{nlm} } = - \frac{{e^2 }}{{2a}}\frac{1}{{\left( 2 \right)^2 }}[/tex]
and therefore I could conclude n=2. But the method took me so long time that it may fail me if I meet this problem in exam time. So if you know any better methods to solve this problem, please let me know. Please enlighten me. Thanks a lot.
Homework Statement
The question is very simple as I stated in the title. "Can you infer the principal quantum number from a given wave function of the hydrogen atom?" Not by memorizing but by logical deduction. I think no one can memorize all of the wave functions of the hydrogen atom.
Homework Equations
For example, you are given this wave function [tex]\psi _{nlm} = \frac{1}{{\sqrt {4\pi } }}\left( {\frac{1}{{2a}}} \right)^{3/2} \left( {2 - \frac{r}{a}} \right)e^{ - r/2a} [/tex]
where[tex]a = \frac{\hbar }{{me^2 }}[/tex]. Of cource, you may know the Hamiltonian that is composed of the kinetic term and the Coulomb potential.
[tex] H = - \frac{{\hbar ^2 }}{{2m}}\nabla ^2 - \frac{{e^2 }}{r} [/tex]
The principal quantum number of above wave equation is 2. But how would you infer it?
The Attempt at a Solution
I tried this method. I know the energy eigenvalue is given by
[tex]E_n = - \frac{{e^2 }}{{2a}}\frac{1}{{n^2 }}[/tex]
So, when I carried out the integration to find the energy eigenvalue, I could obtain
[tex]E_n = \iiint {d^3 r\psi _{nlm}^ * \hat H\psi _{nlm} } = - \frac{{e^2 }}{{2a}}\frac{1}{{\left( 2 \right)^2 }}[/tex]
and therefore I could conclude n=2. But the method took me so long time that it may fail me if I meet this problem in exam time. So if you know any better methods to solve this problem, please let me know. Please enlighten me. Thanks a lot.
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