Excitation of a hydrogen atom by electron collisions

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Homework Help Overview

The problem involves the excitation of a hydrogen atom by a beam of electrons with a kinetic energy of 12.8 eV. The original poster is exploring which visible spectral lines may be emitted as a result of these collisions.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster questions whether the energy from the electron collisions can excite the hydrogen atom to states n=3 or n=2, in addition to n=4. Some participants affirm this possibility and discuss the resulting spectral lines from various transitions.

Discussion Status

Participants are actively discussing the excitation states and the corresponding spectral lines. There is a focus on identifying which transitions produce visible wavelengths, with some guidance provided on checking the wavelengths of the transitions.

Contextual Notes

Participants note the importance of determining which spectral lines fall within the visible range of approximately 3800 to 7500 Angstroms, as specified in the problem.

petermacfarlane
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The problem:
A beam of electrons with kinetic energy 12.8 eV collides with a hydrogen target. What visible spectral lines will be emitted due to collisions?

My question:
I am confident I know how to do the bulk of this question, I am just uncertain about one thing: I know that 12.8 eV is enough energy to excite a ground state electron to n=4. But can a collision from an electron with KE = 12.8 eV excite hydrogen to n=3 or n=2 as well, or must it be the highest energy state?
 
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The answer is clearly yes, it can also excite it to n=3 or n=2 as well as n=4. The spectral lines you see will be the transitions of n=4 to n= 3, n= 4 to n= 2, and n=4 to n= 1, along with n=3 to n= 2, n= 3 to n= 1, and n= 2 to n= 1.
 
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Charles Link said:
The answer is clearly yes, it can also excite it to n=3 or n=2 as well as n=4. The spectral lines you see will be the transitions of n=4 to n= 3, n= 4 to n= 2, and n=4 to n= 1, along with n=3 to n= 2, n= 3 to n= 1, and n= 2 to n= 1.
In addition, it asked what "visible" lines. It appears it wants you to check the wavelengths of each of these transitions to see which ones are between 3800 and 7500 Angstroms or thereabouts...
 
Charles Link said:
In addition, it asked what "visible" lines. It appears it wants you to check the wavelengths of each of these transitions to see which ones are between 3800 and 7500 Angstroms or thereabouts...

Thank you for your help!
 
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