A hydrogenic atom consists of a single electron orbiting a nucleus with Z protons. (Z=1 would be hydrogen itself,Z=2is ionized helium ,Z=3is doubly ionized lithium, and so on.) Determine the Bohr energies En(Z), the binding energyE1(Z), the Bohr radiusa(Z), and the Rydberg constant R(Z)for a hydrogenic atom. (Express your answers as appropriate multiples of the hydrogen values.) Where in the electromagnetic spectrum would the Lyman series fall, for Z=2and Z=3? Hint: There’s nothing much to calculate here— in the potential (Equation 4.52) Ze2, so all you have to do is make the same substitution in all the final results.

V(r)=-e24πo0˙1r (4.52).

Short Answer

Expert verified

The electronic spectrum would be the Lyman seires fall, forz=2 andz=3 is at,z=2 is3.04×10-8m.

At z=3is1.35×10-8m.

Step by step solution

01

Given

The potential is given by:

V(r)=-e24πo0˙1r

02

Electronic spectrum

Consider a hydrogen, if irradiated with light it will be excited to another energy level. The energies of these photons are easily calculated from the Bohr energy formula:

En=-1n2me42h2(4ΤΤ0)2

Lyman lines range fromni=2toni=(withnf=1);

the wavelengths range from

03

Finding the electronic spectrum

1λ2=R1-14=34Rλ2=43R

Down to

role="math" localid="1658210586427" 1λ1=R1-1=RR1=1R

ForZ=2

λ1=14R=14(1.097×107)=2.28×10-8m

to

λ2=13R=3.04×10-8m,

Ultraviolet.

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Most popular questions from this chapter

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.

(a) Using Equation 4.88, work out the first four Laguerre polynomials.

(b) Using Equations 4.86, 4.87, and 4.88, find v(ρ), for the case n=5,I=2.

(c) Find v(ρ)again (for the case role="math" localid="1658315521558" n=5,I=2), but this time get it from the recursion formula (Equation 4.76).

Lq(x)=eqq!(ddx)q(e-x-x9)(4.88)v(ρ)=Ln-2l+1l-1(4.86)Lqp(x)(-1)pddxρLp+q(x)(4.87)cj+1=2(j+l+1-n)(j+1)(j+2l+2)cj(4.76)

(a) If you measured the component of spin angular momentum along the x direction, at time t, what is the probability that you would get +h/2?

(b) Same question, but for the ycomponent.

(c) Same, for the z component.

[Attempt this problem only if you are familiar with vector calculus.] Define the (three-dimensional) probability current by generalization of Problem 1.14:

J=ih2m(ψψ*-ψ*ψ)

(a) Show that satisfies the continuity equation .J=-t|ψ|2which expresses local conservation of probability. It follows (from the divergence theorem) that sJ.da=-ddtv|ψ|2d3rwhere Vis a (fixed) volume and is its boundary surface. In words: The flow of probability out through the surface is equal to the decrease in probability of finding the particle in the volume.

(b) FindJfor hydrogen in the staten=2,l=1,m=1 . Answer:

h64ma5re-r/asinθϕ^

(c) If we interpretmJas the flow of mass, the angular momentum is

L=m(r×J)d3r

Use this to calculate Lzfor the stateψ211, and comment on the result.

Because the three-dimensional harmonic oscillator potential (Equation 4.188)is spherically symmetric, the Schrödinger equation can be handled by separation of variables in spherical coordinates, as well as cartesian coordinates. Use the power series method to solve the radial equation. Find the recursion formula for the coefficients, and determine the allowed energies. Check your answer against Equation4.189.

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