I'm reading about selection rules, and the book is talking about how if you have a parity switching operator in between two wave vectors of opposite (definite) parity, the result is 0. For example, we have(adsbygoogle = window.adsbygoogle || []).push({});

[itex]\left\langle2,0,0 \right|\hat{X}\left|2,0,0\right\rangle = 0[/itex] because [itex]\left|2,0,0\right\rangle[/itex] is of even parity, and X switches its parity (where these kets are the hydrogen wave functions). Then, we have an even parity bra with an odd parity ket, and the result is 0.

My question is, why do these operators switch parity? I'd love to have both a physical and mathematical reason.

Thanks!

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# Why do the X, Y, Z operators switch parity?

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