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Question: Use the virial theorem (Problem 4.40) to prove Equation 6.55.

Short Answer

Expert verified

It is proved that 1r=1an2.

Step by step solution

01

Expression of thepotential energy and Bohr energy

The expression for potential energy is as follows,

V=-e24πo˙01r

The expression for Bohrenergy is as follows,

localid="1658214362022" En=-[m2h2(-e24πo˙0)2]1n2

02

Verification of <1r>=1an2

Write the expression for the relation between potential energy and Bohr energy.

V=2En

Substitute all the values in the above expression.

localid="1658214341492" -e24πo˙01r=-2[m2h2-e24πo˙02]1n2-e24πo˙01r=-2[m2h2e24πo˙02]1n21r=m2h2e24πo˙024πo˙0e21n2=m2h2e24πo˙01n2

Consider a=4πo˙0h2me2, where, a is the Bohr radius.

Substitute4πo˙0h2me2 for a in the above expression.

1r=1an2

Thus, the equation 6.55 is verified.

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Most popular questions from this chapter

For the harmonic oscillator[Vx=1/2kx2], the allowed energies areEN=(n+1/2)ħω,(n=0.1.2,..),whererole="math" localid="1656044150836" ω=k/mis the classical frequency. Now suppose the spring constant increases slightly:k(1+ο')k(Perhaps we cool the spring, so it becomes less flexible.)

(a) Find the exact new energies (trivial, in this case). Expand your formula as a power series inο,, up to second order.

(b) Now calculate the first-order perturbation in the energy, using Equation 6.9. What ishere? Compare your result with part (a).

Hint: It is not necessary - in fact, it is not permitted - to calculate a single integral in doing this problem.

Question: Derive the fine structure formula (Equation 6.66) from the relativistic correction (Equation 6.57) and the spin-orbit coupling (Equation 6.65). Hint: Note tha j=l±12t; treat the plus sign and the minus sign separately, and you'll find that you get the same final answer either way.

Work out the matrix elements of HZ'andHfs'construct the W matrix given in the text, for n = 2.

Suppose we put a delta-function bump in the center of the infinite square well:

H'=αδ(x-a/2)

whereais a constant.

(a) Find the first-order correction to the allowed energies. Explain why the energies are not perturbed for evenn.

(b) Find the first three nonzero terms in the expansion (Equation 6.13) of the correction to the ground state,Ψ11.

Question: The most prominent feature of the hydrogen spectrum in the visible region is the red Balmer line, coming from the transition n = 3to n = 2. First of all, determine the wavelength and frequency of this line according to the Bohr Theory. Fine structure splits this line into several closely spaced lines; the question is: How many, and what is their spacing? Hint: First determine how many sublevels the n = 2level splits into, and find Efs1for each of these, in eV. Then do the same for n = 3. Draw an energy level diagram showing all possible transitions from n = 3to n = 2. The energy released (in the form of a photon) is role="math" localid="1658311193797" (E3-E2)+E, the first part being common to all of them, and the E(due to fine structure) varying from one transition to the next. Find E(in eV) for each transition. Finally, convert to photon frequency, and determine the spacing between adjacent spectral lines (in Hz- -not the frequency interval between each line and the unperturbed line (which is, of course, unobservable), but the frequency interval between each line and the next one. Your final answer should take the form: "The red Balmer line splits into (???)lines. In order of increasing frequency, they come from the transitionsto (1) j =(???),toj =(???) ,(2) j =(???) to j =(???)……. The frequency spacing between line (1)and line (2)is (???) Hz, the spacing between line (2)and (3) line (???) Hzis……..”

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