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A hydrogen atom electron is in a 2p state. If no experiment has been done to establish a z-component of angular momentum, the atom is equally likely to be found with any allowed value of LZ. Show that if the probability densities for these different possible states are added (with equal weighting), the result is independent of both ϕandθ

Short Answer

Expert verified

The probability densities for these different possible states are independent of ϕandθ

Step by step solution

01

 Angular momentum

Angular momentum is defined as the product of the angular velocity and its moment of inertia.

02

 Given data

The state of the hydrogen atom is 2p.

03

Show the probability densities are independent of and

We already know that the probability density does not depend on the azimuthal angleφ. In the absence of information about the z−component of angular momentum it is equally likely that the electron would have any of the allowed values. Adding the angular probability densities with equal weights, we have

Θ1.0(θ)+Θ1.+1(θ)+Θ1.-1(θ)=34πcosθ2+38πsinθ2+38πsinθ2=34πcos2θ+238πsin2θ=34π

Where,θ = colatitude angle,ϕ = azimuth angle

This has no dependence on either ϕorθ

This is clear that the above-mentioned expression is independent of θandϕ

Hence, the probability densities for these different possible states are independent of ϕand θ

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Most popular questions from this chapter

Spectral lines are fuzzy due to two effects: Doppler broadening and the uncertainty principle. The relative variation in wavelength due to the first effect (see Exercise 2.57) is given by

∆λλ=3kBT/mc

Where T is the temperature of the sample and m is the mass of the particles emitting the light. The variation due to the second effect (see Exercise 4.72) is given by

∆λλ=λ4Ï€³¦

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(a) Suppose the hydrogen in a star has a temperature of 5×104K. Compare the broadening of these two effects for the first line in the Balmer series (i.e.,ni=3→nf=2 ). Assume a transition time of 10-8s. Which effect is more important?

(b) Under what condition(s) might the other effect predominate?

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Since this is a central force, we may use the Schrodinger equation in the form (7-30)-that is, just before the specific hydrogen atom potential energy is inserted. Show that the following is a solution

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Now apply the appropriate boundary conditions. and in so doing, find the allowed angular momenta and energies for solutions of this form.

In section 7.5,eimlφis presented a sour preferred solution to the azimuthal equation, but there is more general one that need not violate the smoothness condition, and that in fact covers not only complex exponentials but also suitable redelinitions of multiplicative constants, sine, and cosine,

Φm1(Φ)=Ae+imlφ+Be+imlφ

(a) Show that the complex square of this function is not, in general, independent of φ.

(b) What conditions must be met by A and/or B for the probability density to be rotationally symmetric – that is, independent of φ ?

Knowing precisely all components of a nonzero L→would violate the uncertainty principle, but knowingthat L→is precisely zerodoes not. Why not?

(Hint:For l=0 states, the momentum vector p→ is radial.)

Here we Pursue the more rigorous approach to the claim that the property quantized according to ml is Lz,

(a) Starting with a straightforward application of the chain rule,

∂∂φ = ∂x∂φ/∂∂x+∂y∂φ∂∂y+∂z∂φ∂∂z

Use the transformations given in Table 7.2 to show that

∂∂φ = -y∂∂x+x∂∂y

(b) Recall that L = r x p. From the z-component of this famous formula and the definition of operators for px and py, argue that the operator for Lz is -ih∂∂φ..

(c) What now allows us to say that our azimuthal solutioneimlφ has a well-defined z-component of angular momentum and that is value mlh.

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