In Problem4.3 you showed that Y21(θ,ϕ)=-15/8πsinθcosθeiϕ. Apply the raising operator to find localid="1656065252558" Y22(θ,ϕ). Use Equation 4.121to get the normalization.

Short Answer

Expert verified

The value ofY22θ,ϕis14152πheiϕsinθ2.

Step by step solution

01

Define Raising Operator

An operator that raises or lowers the eigenvalue of another operator (collectively called as ladder operators) is referred to as a raising or lowering operator.

02

Find the value of Y22(θ,ϕ)

In this step evaluate first the spherical harmonic is Y21θ,ϕ.

From problem 4.3, the value of Y21

Y21=-158ττsinθcosθeioL+=heiϕθ+icotθϕL+Y21=Y22

Now, determine the spherical harmonic Y22θ,ϕas follows,

localid="1658464225727" Y21=-158πheiϕeiϕ)(sinθcosθ)θ+icotθsinθcosθeiϕϕ=-158πheiϕeiϕ(cos2θ-sin2θ)+icotθsinθcosθ(ieiϕ)=-158πheiϕcos2θ-cos2θeiϕ=152πhe2iϕsin2θ=12152πh(e2iϕsinθ)2

Thus, the value ofY22θ,ϕislocalid="1658464244244" 12152πheiϕsin2θ2.

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Most popular questions from this chapter

[Refer to Problem 4.59 for background.] In classical electrodynamics the potentials Aandφare not uniquely determined; 47 the physical quantities are the fields, E and B.

(a) Show that the potentials

φ'φ-Λt,A'A+Λ

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(b) In quantum mechanics the potentials play a more direct role, and it is of interest to know whether the theory remains gauge invariant. Show that

Ψ'eiqΛ/Ψ

satisfies the Schrödinger equation (4.205) with the gauge-transformed potentialsφ'andA', SinceΨ'differs fromψonly by a phase factor, it represents the same physical state, 48and the theory is gauge invariant (see Section 10.2.3for further discussion).

(a) For a functionf(ϕ)that can be expanded in a Taylor series, show that f(ϕ+φ)=eiLzφ/f(ϕ) (where is an arbitrary angle). For this reason, Lz/ is called the generator of rotations about the Z-axis. Hint: Use Equation 4.129 , and refer Problem 3.39.More generally, L·n^/ is the generator of rotations about the direction n^, in the sense that exp(iL·n^φ/)effects a rotation through angleφ (in the right-hand sense) about the axis n^ . In the case of spin, the generator of rotations is S·n^/. In particular, for spin 1/2 χ'=ei(σ·n^)φ/2χtells us how spinors rotate.

(b) Construct the (2×2)matrix representing rotation by 180about the X-axis, and show that it converts "spin up" χ+into "spin down"χ- , as you would expect.

(c) Construct the matrix representing rotation by 90about the Y-axis, and check what it does to

χ+

(d) Construct the matrix representing rotation by 360about the -Zaxis, If the answer is not quite what you expected, discuss its implications.

(e) Show thatei(σ·n^)φ/2=cos(φ/2)+i(n^·σ)sin(φ/2)

Use equations 4.27 4.28 and 4.32 to constructy00,y21Check that they are normalized and orthogonal

A hydrogen atom starts out in the following linear combination of the stationary states n=2, l=1, m=1 and n=2, l=1, m=-1.

ψ(r,0)=12(ψ211+ψ21-1)

(a) Constructψ(r,t)Simplify it as much as you can.

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