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(a) A particle of spin1and a particle of spin 2 are at rest in a configuration such that the total spin is 3, and its z component is . If you measured the z component of the angular momentum of the spin-2particle, what values might you get, and what is the probability of each one?

(b) An electron with spin down is in the state510of the hydrogen atom. If you could measure the total angular momentum squared of the electron alone (not including the proton spin), what values might you get, and what is the probability of each?

Short Answer

Expert verified

(a) 2with a probability equal to 1/15 , or with a probability of 8/15 or with a probability of 6/15 .

(b) The total is 3/2 or 1/2 withl(l+1)2=1542 and 342respectively. Also, for 1542the probability is 2/3 , and for 342it is 1/3 .

Step by step solution

01

Definition of Probability

The probability of an event occurring. The proportion of the total number of conceivable outcomes to the number of options in an exhaustive collection of equally likely outcomes that cause a given occurrence.

02

(a) Solve the total spin is 3, and its z  component is ℏ

Expand the composite spin 3,1>from the individual spins. For spin 2, the expected states are as follows,

|2,2>,|2,1>,|2,0>,|2,-1>, and 2,-2>.

Write the possible states for spin 1.

localid="1658127583657" |1,1>,|1,0>,and1,-1>.

The combinations that have a z projection equal to one are needed, so the expansion can be written as follows,

|3,1=|2,2>|1,-1>+|2,1>|1,0>+|2,0>|1,1

Determine the three expansion coefficients a , and in the Clebsch-Gordon tables. Then the probabilities are ||2,||2 and 2.

Return to the Clebsch-Gorden table and using the equation.

|sm=cm1m2mm1+m2=ms1s2s|s1m1>|s2m2>

Write the outcomes using the above information.

|31=115|22>|1-1>+815|21>|(100)+615|2011

Thus, 2 is obtained with a probability equal to 1/15 , orwith a probability of 8/15 or with a probability of 6/15 .

03

(b) Determination of the total angular momentum squared of the electron

Look the table 11/2 and write the outcome.

|10|12-12=2334-12+1312-12

So the total is 3/2 or 1/2 with l(l+1)2=1542and 342respectively.

Thus, for 1542the probability is 2/3 , and for 342it is 1/3 .

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Most popular questions from this chapter

What is the most probable value of r, in the ground state of hydrogen? (The answer is not zero!) Hint: First you must figure out the probability that the electron would be found between r and r + dr.

Consider the three-dimensional harmonic oscillator, for which the potential is

V(r)=12尘蝇2r2

(a) Show that separation of variables in cartesian coordinates turns this into three one-dimensional oscillators, and exploit your knowledge of the latter to determine the allowed energies. Answer:

En=(n+3/2)h

(b) Determine the degeneracyofd(n)ofEn.

An electron is at rest in an oscillating magnetic field

B=B0cos(蝇t)k^

whereB0 and are constants.

(a) Construct the Hamiltonian matrix for this system.

(b) The electron starts out (at t=0 ) in the spin-up state with respect to the x-axis (that is:(0)=+(x)). Determine X(t)at any subsequent time. Beware: This is a time-dependent Hamiltonian, so you cannot get in the usual way from stationary states. Fortunately, in this case you can solve the timedependent Schr枚dinger equation (Equation 4.162) directly.

(c) Find the probability of getting-h/2 , if you measure Sx. Answer:

sin2(纬叠02sin(蝇t))

(d) What is the minimum field(B0) required to force a complete flip inSx ?

A particle of mass m is placed in a finite spherical well:

V(r)={-V0,ra;0,r>a;

Find the ground state, by solving the radial equation withl=0. Show that there is no bound state if V0a2<2k2/8m.

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鈥檚 nothing much to calculate here鈥 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)=-e24o01r (4.52).

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