Confusing eigensolutions of a wave function

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Discussion Overview

The discussion revolves around the eigensolutions of a wave function in a potential cavity defined by a delta function. Participants explore the mathematical formulation of the wave function, particularly focusing on the eigenfunction's behavior in different regions and the implications of parameters such as amplitude and phase angle.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant presents a potential cavity defined by a piecewise function and questions the nature of the eigenfunction in the second region, specifically regarding the amplitude being 1 and the presence of a phase angle.
  • The same participant inquires whether the wave function can be referred to as an "excitation mode."
  • Other participants remind the original poster to adhere to forum guidelines by posting in the homework section and using the required template.
  • There is a clarification that with a positive omega, the scenario described represents a delta barrier rather than a cavity.

Areas of Agreement / Disagreement

Participants generally agree on the need for proper forum etiquette and the classification of the potential as a delta barrier. However, the original poster's questions about the wave function's characteristics remain unresolved, indicating a lack of consensus on those specific points.

Contextual Notes

The discussion does not resolve the mathematical implications of the amplitude and phase angle in the wave function, nor does it clarify the terminology regarding "excitation mode." There may be missing assumptions regarding the definitions of terms used in the context of the potential.

Yourong Zang
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Consider a potential cavity
$$V(r)=\begin{cases}\infty, &x\in(-\infty,0]\\\frac{\hslash^2}{m}\Omega\delta(x-a), &x\in(0,\infty)\end{cases}$$
The eigenfunction of the wave function in this field suffices
$$-\frac{\hslash^2}{2m}\frac{d^2\psi}{dx^2}+\frac{\hslash^2}{m}\Omega\delta(x-a)\psi=E\psi$$
A textbook gives the following solution:
$$\psi(x)=\begin{cases}Asin(kx), &x\in(0,a)\\ sin(kx+\phi), &x\in(a,\infty)\end{cases}$$
where
$$k^2=\frac{2mE}{\hslash^2}$$
I can clearly understand the first part but in the second part, why is the amplitude of the function 1 and why is there a phase angle?

And is this wave
$$\psi(x)=\sin(kx+\phi)$$
called something like the "excitation mode"?
 
Last edited by a moderator:
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Hello Yourong Zang, ##\qquad## :welcome: ##\qquad## !

Please post this kind of questions in the homework forum and use the template -- it's mandatory, see guidelines

Your problem is worked out here With a positive omega you have a delta barrier, not a cavity.
 
Last edited by a moderator:
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BvU said:
Hello Yourong Zang, ##\qquad## :welcome: ##\qquad## !

Please post this kind of questions in the homework forum and use the template -- it's mandatory, see guidelines

Your problem is worked out here With a positive omega you have a delta barrier, not a cavity.
Thank you.
 

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