Finding the probability density function given the eigenfunction

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The discussion focuses on finding the probability density function from a given eigenfunction, specifically the wave function ψ=C exp( (ipx/ħ) - (x²/2a²) ). The user initially struggled with squaring the function due to a complex integral but later realized that the imaginary part cancels out when squared. The squared wave function simplifies to |ψ(x)|² = C² exp(-x²/a²), leading to the identification of a Gaussian distribution. The user then outlines the steps to find the normalization constant by integrating the probability density over all space and setting it equal to one. The final expression for the normalization constant is C = 1/(√a π^(1/4)).
ypal
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Homework Statement



I need to find the probability density function given the eigenfunction

Homework Equations



\psi=C\exp^({\frac{ipx}{\hbar}-\frac{x^2}{2a^2}})

The Attempt at a Solution



I tried to square the function but that gave me a nasty integral that I could not solve. I also tried to factorise the index so I could've used change of variables for the Gaussian integral. I haven't come across such a question before so I am not quite sure what to do. Please help me.
Cheers
 
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The probability density is given by
P(x)=|\psi(x)|^2.
Here \psi is the wave function of the particle. Calculate this square, and you'll find a pretty well-known probability distribution!
 
I've realized my mistake...face palm -_- Thanks! But I can't make progress at this point.
Edit: I need the integral to find the normalisation constant, not for the actual density function. The thing that worries me is the x^2 and x term being together at the index.
 
Last edited:
ypal said:
I need the integral to find the normalisation constant, not for the actual density function. The thing that worries me is the x^2 and x term being together at the index.
Show details of your attempt to perform the integral.
 
ypal said:

Homework Statement



I need to find the probability density function given the eigenfunction

Homework Equations



\psi=C\exp^({\frac{ipx}{\hbar}-\frac{x^2}{2a^2}})

The Attempt at a Solution



I tried to square the function but that gave me a nasty integral that I could not solve. I also tried to factorise the index so I could've used change of variables for the Gaussian integral. I haven't come across such a question before so I am not quite sure what to do. Please help me.
Cheers

Hey Guys!
I've made some progress and everything looks neat. It turns out the imaginary part vanishes when the function is squared(due to its conjugate). If someone could verify my work I'd appreciate it. Thanks!
\psi=C\exp^({\frac{ipx}{\hbar}-\frac{x^2}{2a^2}})
|\psi(x)|^2=C^2 exp^{\frac{ipx}{\hbar}-\frac{x^2}{2a^2}} . exp^{\frac{-ipx}{\hbar}-\frac{x^2}{2a^2}}
|\psi(x)|^2=C^2 exp^{-\frac{x^2}{a^2}}
Let \beta=\frac{1}{a^2}, |\psi(x)|^2=C^2 exp^{-\beta x^2}

Now I need to integrate this from -\infty to \infty and equate to 1 in order to find the normalisation constant.
C^{2}\int_{-\infty}^{\infty} exp^{-\beta x^2}=1
C^{2}\sqrt{\frac{\pi}{\beta}}=1
C^{2}=\sqrt{\frac{\beta}{\pi}}→ C=\frac{1}{\sqrt{a}\pi^{\frac{1}{4}}}

I am new to Latex...so I'm trying my best :D
 

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