/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Q25E Question: Consider a cubic 3D in... [FREE SOLUTION] | 91影视

91影视

Question: Consider a cubic 3D infinite well of side length of L. There are 15 identical particles of mass m in the well, but for whatever reason, no more than two particles can have the same wave function. (a) What is the lowest possible total energy? (b) In this minimum total energy state, at what point(s) would the highest energy particle most likely be found? (Knowing no more than its energy, the highest energy particle might be in any of multiple wave functions open to it and with equal probability.)

Short Answer

Expert verified

Answer

(a) The lowest possible total energy is 1072h22mL2.

(b) The highest energy particle is most likely to found at the centre of the well.

Step by step solution

01

Identification of given data

The side length of 3D well is L.

The number of identical particles is n = 15 .

The mass of the identical particles is m.

The lowest energy wave function has nx,ny,nz=1,1,1. The next two lowest have (2,1,1), (1,2,1) and (1,1,2) . By combining each from these two there will six pairs for adding in existing two. Next higher will be (2,2,1) ,(2,1,2) and (1,2,2). This adds six to existing eight states. The fifteenth state is(3,1,1) ,(1,3,1) and (1,1,3) . for the last particle

02

Step 2(a): Determination of lowest possible total energy

The lowest possible total energy is given as:

Et=nx2+ny2+nz22h22mL2

Here, h is the Planck鈥檚 constant.

Substitute all the values in the above equation.

Et=212+12+12+622+12+12+622+22+12+32+12+122h22mL2\hfillEt=1072h22mL2

Therefore, the lowest possible total energy is 1072h22mL2.

03

Step 3(b): Determination of point for highest energy particles

Two among the three quantum numbers are unity, which gives maximum wave function at the centre of 3D well. The other quantum number is three for which there will be three maxima. This indicates that particle is most likely found at three points. The probability of finding particle is at the centre of the 3D well.

Therefore, the highest energy particle is most likely to found at the centre of the well.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91影视!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

An electron in a hydrogen atom is in the (n,l,ml) = (2,1,0) state.

(a) Calculate the probability that it would be found within 60 degrees of z-axis, irrespective of radius.

(b) Calculate the probability that it would be found between r = 2a0 and r = 6a0, irrespective of angle.

(c) What is the probability that it would be found within 60 degrees of the z-axis and between r = 2a0 and r = 6a0?

The Diatomic Molecule: Exercise 80 discusses the idea of reduced mass. Classically or quantum mechanically, we can digest the behavior of a two-particle system into motion of the center of mass and motion relative to the center of mass. Our interest here is the relative motion, which becomes a one-particle problem if we merely use for the mass for that particle. Given this simplification, the quantum-mechanical results we have learned go a long way toward describing the diatomic molecule. To a good approximation, the force between the bound atoms is like an ideal spring whose potential energy is 12kx2, where x is the deviation of the atomic separation from its equilibrium value, which we designate with an a. Thus,x=r-a . Because the force is always along the line connecting the two atoms, it is a central force, so the angular parts of the Schr枚dinger equation are exactly as for hydrogen, (a) In the remaining radial equation (7- 30), insert the potential energy 12kx2and replace the electron massm with . Then, with the definition.f(r)=rR(r), show that it can be rewritten as

-22d2dr2f(r)+2I(I+1)2r2f(r)+12kx2f(r)=Ef(r)

With the further definition show that this becomes

-22d2dx2g(x)+2I(I+1)2(x+a)g(x)+12kx2g(x)=Eg(x)

(b) Assume, as is quite often the case, that the deviation of the atoms from their equilibrium separation is very small compared to that separation鈥攖hat is,x<<a. Show that your result from part (a) can be rearranged into a rather familiar- form, from which it follows that
E=(n+12)k+2I(I+1)2a2n=0,1,2,...I=0,1,2,...

(c)

Identify what each of the two terms represents physically.

If the constantCxinequation(7-5)were positive, the general mathematical solution would be

Ae+cxx+Be-cxx

Show that this function cannot be 0 at two points. This makes it an unacceptable solution for the infinite well, since it cannot be continuous with the wave functions outside the walls, which are 0.

A spherical infinite well has potential energy

U(r)={0r<a+r>a

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

R(r)=Asinbrr

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

Consider a cubic 3D infinite well.

(a) How many different wave functions have the same energy as the one for which (nx,ny,nz)=(5,1,1)?

(b) Into how many different energy levels would this level split if the length of one side were increased by 5% ?

(c) Make a scale diagram, similar to Figure 3, illustrating the energy splitting of the previously degenerate wave functions.

(d) Is there any degeneracy left? If so, how might it be 鈥渄estroyed鈥?

See all solutions

Recommended explanations on Physics Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.