- #1
svletana
- 21
- 1
Hello! I have the following problem I'm trying to solve:
An Hydrogen atom in the state |100> is found between the plates of a capacitor, where the electric field (weak and uniform) is: [itex]E(t) = \epsilon e^{-\alpha t / \tau}[/itex].
Calculate the parameters of the potential ([itex]\epsilon, \alpha, \tau[/itex]) so that for a time [itex]t \gg \tau[/itex] the transition probability to any of the n=2 states is equal to 0.1.
The field is asumed to be in an arbitrary [itex]r = (x,y,z)[/itex] direction, so that [itex]W = \epsilon e^{-\alpha t / \tau} r[/itex].
The formula for transition probability is (using atomic units):
[tex]P = \left| \int_0^{T \gg \tau} e^{i \omega t} <100 | r | 21m> \epsilon e^{-\alpha t / \tau}dt \right|^2[/tex]
where [itex]\omega = \frac{E_{21m} - E_{100}}{\hbar} = \frac{-3}{4} [/itex].
For the [itex]<100|r|21m>[/itex] elements we have the results, for each m:
[tex]<100|r|200> = 0[/tex]
[tex]<100|r|210> = \frac{2^7 \sqrt{2} \hat{z}}{3^5}[/tex]
[tex]<100|r|21\pm1> = \frac{2^7}{3^5}(\mp\hat{x} - i\hat{y})[/tex]
I solved the integral for an arbitrary m and l=1, calling the result of the [itex]<100|r|21m>=\gamma[/itex]. Since it does not depend on t we can take it out of the integral along with all the constants. The integral is then:
[tex]P = \gamma^2 \epsilon^2 \left| \int_0^{T \gg \tau} e^{-\left( \frac{3i}{4} + \frac{\alpha}{\tau}\right)t} dt \right|^2[/tex]
For which I solved and took the limit [itex]T \rightarrow \infty[/itex] and got the result:
[tex]\frac{\gamma^2 \epsilon^2}{\frac{9}{16} + \frac{\alpha^2}{\tau^2}}[/tex]
Now, [itex]\gamma^2 = \frac{2^{15}}{3^{10}}[/itex] for any value of m. And that result must be equal to 0.1 according to the guidelines.
I don't see how I could possibly calculate 3 parameters from this equation, what am I missing? Thanks in advance!
Homework Statement
An Hydrogen atom in the state |100> is found between the plates of a capacitor, where the electric field (weak and uniform) is: [itex]E(t) = \epsilon e^{-\alpha t / \tau}[/itex].
Calculate the parameters of the potential ([itex]\epsilon, \alpha, \tau[/itex]) so that for a time [itex]t \gg \tau[/itex] the transition probability to any of the n=2 states is equal to 0.1.
Homework Equations
The field is asumed to be in an arbitrary [itex]r = (x,y,z)[/itex] direction, so that [itex]W = \epsilon e^{-\alpha t / \tau} r[/itex].
The formula for transition probability is (using atomic units):
[tex]P = \left| \int_0^{T \gg \tau} e^{i \omega t} <100 | r | 21m> \epsilon e^{-\alpha t / \tau}dt \right|^2[/tex]
where [itex]\omega = \frac{E_{21m} - E_{100}}{\hbar} = \frac{-3}{4} [/itex].
For the [itex]<100|r|21m>[/itex] elements we have the results, for each m:
[tex]<100|r|200> = 0[/tex]
[tex]<100|r|210> = \frac{2^7 \sqrt{2} \hat{z}}{3^5}[/tex]
[tex]<100|r|21\pm1> = \frac{2^7}{3^5}(\mp\hat{x} - i\hat{y})[/tex]
The Attempt at a Solution
I solved the integral for an arbitrary m and l=1, calling the result of the [itex]<100|r|21m>=\gamma[/itex]. Since it does not depend on t we can take it out of the integral along with all the constants. The integral is then:
[tex]P = \gamma^2 \epsilon^2 \left| \int_0^{T \gg \tau} e^{-\left( \frac{3i}{4} + \frac{\alpha}{\tau}\right)t} dt \right|^2[/tex]
For which I solved and took the limit [itex]T \rightarrow \infty[/itex] and got the result:
[tex]\frac{\gamma^2 \epsilon^2}{\frac{9}{16} + \frac{\alpha^2}{\tau^2}}[/tex]
Now, [itex]\gamma^2 = \frac{2^{15}}{3^{10}}[/itex] for any value of m. And that result must be equal to 0.1 according to the guidelines.
I don't see how I could possibly calculate 3 parameters from this equation, what am I missing? Thanks in advance!