EV per Torr*cm -- What does it mean?

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SUMMARY

The discussion centers on the concept of "eV per Torr*cm," specifically in relation to nitrogen gas and its application in laser technology. This unit represents an ionization constant that connects electric field strength to the energy required for ionization, as outlined by Paschen’s Law. The energy per collision is influenced by the mean free path length, which is inversely proportional to pressure. The constant is crucial for determining the energy necessary to excite the lasing state, rather than merely the minimum energy for discharge.

PREREQUISITES
  • Understanding of Paschen’s Law and its implications in gas ionization
  • Familiarity with laser physics and the principles of energy excitation
  • Knowledge of SI units and their conversions, particularly in the context of pressure and energy
  • Basic grasp of electric field strength and its relationship to particle acceleration
NEXT STEPS
  • Research the implications of Paschen’s Law in different gases beyond nitrogen
  • Explore the role of electric field strength in laser discharge mechanisms
  • Learn about the calculations involved in converting eV per Torr*cm to other energy units
  • Investigate advanced laser technologies and their dependence on ionization constants
USEFUL FOR

Physicists, laser engineers, and anyone involved in the study or application of gas ionization and laser technology will benefit from this discussion.

DariusP
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I was reading about this
https://en.wikipedia.org/wiki/Nitrogen_laser

and it says "80 to 100 eV per Torr*cm pressure of nitrogen gas". I'm finding this a little bit confusing. It needs some specific amount of energy in a centimeter of volume with 1 Torr of pressure?
 
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I don’t see that in the article, but I can explain the unit.

That is an ionization constant. See the wiki article on Paschen’s Law:
https://en.m.wikipedia.org/wiki/Paschen's_law
This constant relates the electric field strength to the energy per collision required to cause ionization and so sustain a discharge. The pressure is in there because the energy accumulated by a particle depends on the distance over which it is accelerated by the field, so the energy per collision depends on the mean free path length which is inversely proportional to the pressure.

Note that for a laser this constant is not necessarily for the minimum energy for discharge, but sets the energy per collision high enough to excite the lasing state.
 
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Cutter Ketch said:
I don’t see that in the article, but I can explain the unit.

That is an ionization constant. See the wiki article on Paschen’s Law:
https://en.m.wikipedia.org/wiki/Paschen's_law
This constant relates the electric field strength to the energy per collision required to cause ionization and so sustain a discharge. The pressure is in there because the energy accumulated by a particle depends on the distance over which it is accelerated by the field, so the energy per collision depends on the mean free path length which is inversely proportional to the pressure.

Note that for a laser this constant is not necessarily for the minimum energy for discharge, but sets the energy per collision high enough to excite the lasing state.
Love you, thank you very much
 
it is in surface area units. In SI units it is
eV per Torr*cm=##\frac{q_e*V}{Torr*cm}=\frac{1.60217646*10^{-19}*C*V}{133.322*Pa*m/100}=\frac{1.60217646*10^{-17}*C*V}{133.322*N/m}=1.2017344924318567*10^{-19}*m^2##
 

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