What is the Parity of a System Described by a Wavefunction?

In summary, The conversation discusses the wavefunction of a system and finding its parity. The attempt at a solution is incorrect, but is corrected by realizing that the parity operator in spherical coordinates does not change the direction of the vector. This leads to the correct answer of odd parity.
  • #1
humanist rho
95
0

Homework Statement


The wavefunction describing state of a system is,
[tex]\psi (r,\theta ,\phi )=\frac{1}{8\sqrt{\pi }}\left( \frac{1}{a_{0}}%
\right) ^{3/2}\frac{r}{a_{0}}e^{-4/2a_{0}}\sin \theta e^{-i\phi }[/tex]
Find the parity of system in this state.


The Attempt at a Solution



[tex]\psi (-r,\theta ,\phi )=\frac{1}{8\sqrt{\pi }}\left( \frac{1}{a_{0}}%
\right) ^{3/2}\frac{-r}{a_{0}}e^{-4/2a_{0}}\sin \theta e^{-i\phi }
=-\psi (r,\theta ,\phi )[/tex]
odd parity.


I'm wrong.But donno where. Pls help.
 
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  • #2
In spherical coordinates, the parity operator takes
\begin{align*}
r &\to r \\
\theta &\to \pi-\theta \\
\phi &\to \phi+\pi
\end{align*}
 
  • #3
you mean r →-r ?

Then that gives me the perfect answer.
Thank you very much dear friend.
 
  • #4
No, r goes to +r.
 
  • #5
How is that possible?
is it bcz r^2 = x^2+y^2+z^2?
But the reflection changes direction of vector also na?

Can you please explain?
 
  • #6
humanist rho said:
But the reflection changes direction of vector also na?
What?
 

FAQ: What is the Parity of a System Described by a Wavefunction?

What is the parity of a wavefunction?

The parity of a wavefunction is a measure of its symmetry. It determines whether the wavefunction is even or odd under spatial inversion, which is the process of flipping the coordinates of all particles in the system. A wavefunction with even parity remains unchanged under spatial inversion, while a wavefunction with odd parity changes sign.

How is the parity of a wavefunction determined?

The parity of a wavefunction is determined by its spatial dependence. If the wavefunction is symmetric with respect to spatial inversion, it has even parity. If the wavefunction is anti-symmetric, it has odd parity. In mathematical terms, the parity of a wavefunction is determined by the sign of the wavefunction at a point when its coordinates are inverted.

What is the significance of parity in quantum mechanics?

In quantum mechanics, parity is an important concept that helps us understand the behavior of systems and particles. It is a fundamental property that affects the selection rules for certain physical processes, such as transitions between energy levels. Parity also plays a role in determining the quantum numbers of particles and the allowed states of a system.

Can the parity of a wavefunction change?

Yes, the parity of a wavefunction can change depending on its interactions with other particles or external fields. For example, in a system of two particles, if one particle has even parity and the other has odd parity, the overall parity of the system will change when the particles interact. Additionally, the parity of a wavefunction can also change under certain transformations, such as rotation or reflection.

How does the parity of a wavefunction affect physical observables?

The parity of a wavefunction affects the selection rules for physical observables. For example, in a system with even parity, only even values of angular momentum are allowed, while in a system with odd parity, only odd values of angular momentum are allowed. This has important implications for the properties and behavior of particles and systems in quantum mechanics.

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