How Do You Calculate the Normalization Constant for Radial Wave Functions?

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Discussion Overview

The discussion revolves around the calculation of the normalization constant for radial wave functions, specifically focusing on the normalization process and the evaluation of integrals involved in this context. Participants explore the mathematical steps necessary to achieve normalization and the challenges faced in obtaining numerical values from integrals.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant expresses confusion about the normalization process for radial wave functions and the specific integral involved.
  • Another participant clarifies that the extra r^2 factor arises from the volume element in spherical-polar coordinates and emphasizes the importance of definite integrals.
  • A participant confirms the integration limits are from 0 to infinity, questioning how this affects the numerical outcome.
  • There is a suggestion to evaluate the integral of z^4e^{-z} and to consider constant terms in the calculation.
  • One participant reports using Mathematica to obtain a numerical result of 24 for the integral, while expressing a preference for manual calculation.
  • A suggestion is made to use a specific technique involving differentiation under the integral sign to solve the integral.
  • Another participant hints at using integration by parts as a method to tackle the integral more effectively.

Areas of Agreement / Disagreement

Participants generally agree on the normalization process and the need for definite integrals, but there is no consensus on the best method to evaluate the integral or the specific numerical results, as some participants prefer manual methods while others use computational tools.

Contextual Notes

Participants have not fully resolved the steps necessary to compute the integral by hand, and there are references to different techniques that may or may not lead to the same numerical results.

Khaleesi
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Hi, so I'm having a bit of trouble understanding the normalization of radial waves. I understand that the equation is the integral of ((R^2)r^2)=1 but I'm not understanding how the process works. I need the normalization constant on R32. I got the function to come out to be (((r^2)(Co)(e^(-r/3a))/(27a^3)) so I can take that and plug it into the normalization equation (with r/a=z) to get ((Co)/(27a^3)^2) (a^4) integral of (z^2)(e^(-z))(z^2)dz then I combined both the z^2's so it's now the stuff out front integral of ((z^4)(e^(-z))dz and this is where I'm stuck. From what I keep seeing is that people are getting actual numerical values and I don't understand how that part works. Please help.
 
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The process is the same as when you normalize any wavefunction - the extra r^2 comes from the volume element for spherical-polar coordinates.
You get the numerical values because it is a definite integral. What are the limits of the integration?
 
Simon Bridge said:
The process is the same as when you normalize any wavefunction - the extra r^2 comes from the volume element for spherical-polar coordinates.
You get the numerical values because it is a definite integral. What are the limits of the integration?
Well the initial equation states that it's from 0 to infinity. That's were I don't see an actual value coming into place. Unless the bounds somehow change?
 
Lets makes sure I follow you - you are trying to evaluate $$\int_0^\infty z^4e^{-z}\;dz$$ ... with a bunch of constant terms out the front?
If so - then what do you get for the indefinite integral?
 
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Simon Bridge said:
Lets makes sure I follow you - you are trying to evaluate $$\int_0^\infty z^4e^{-z}\;dz$$ ... with a bunch of constant terms out the front?
If so - then what do you get for the indefinite integral?
Yes. And I just plugged it in on mathematica and got an answer of 24. I was trying to do it by hand because I hate taking the easy way out, but thanks so much for responding!
 
There is a particular trick for solving integrals of this type. Try computing
$$
\int_0^\infty e^{-st} dt
$$
and then differentiate wrt ##s## a few times.
 
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I was trying to do it by hand because I hate taking the easy way out.
... hint: integration by parts.
You need to do the "by parts" trick more than once.
 

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