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

  • I
  • Thread starter Thread starter DariusP
  • Start date Start date
  • Tags Tags
    Ev Mean Per
AI Thread Summary
The discussion centers on the energy requirements for nitrogen lasers, specifically the 80 to 100 eV per Torr*cm pressure of nitrogen gas. This value represents an ionization constant related to Paschen's Law, which connects electric field strength to the energy needed for ionization and sustaining a discharge. The pressure factor is crucial as it influences the mean free path length, affecting energy per collision. Additionally, the energy specified is not just for discharge but is sufficient to excite the lasing state. The conversion to SI units is also clarified, emphasizing its relevance in understanding the energy dynamics in laser operation.
DariusP
Messages
50
Reaction score
3
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?
 
Physics news on Phys.org
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.
 
  • Like
Likes DariusP
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##
 
Consider an extremely long and perfectly calibrated scale. A car with a mass of 1000 kg is placed on it, and the scale registers this weight accurately. Now, suppose the car begins to move, reaching very high speeds. Neglecting air resistance and rolling friction, if the car attains, for example, a velocity of 500 km/h, will the scale still indicate a weight corresponding to 1000 kg, or will the measured value decrease as a result of the motion? In a second scenario, imagine a person with a...
Scalar and vector potentials in Coulomb gauge Assume Coulomb gauge so that $$\nabla \cdot \mathbf{A}=0.\tag{1}$$ The scalar potential ##\phi## is described by Poisson's equation $$\nabla^2 \phi = -\frac{\rho}{\varepsilon_0}\tag{2}$$ which has the instantaneous general solution given by $$\phi(\mathbf{r},t)=\frac{1}{4\pi\varepsilon_0}\int \frac{\rho(\mathbf{r}',t)}{|\mathbf{r}-\mathbf{r}'|}d^3r'.\tag{3}$$ In Coulomb gauge the vector potential ##\mathbf{A}## is given by...
Thread 'Griffith, Electrodynamics, 4th Edition, Example 4.8. (First part)'
I am reading the Griffith, Electrodynamics book, 4th edition, Example 4.8 and stuck at some statements. It's little bit confused. > Example 4.8. Suppose the entire region below the plane ##z=0## in Fig. 4.28 is filled with uniform linear dielectric material of susceptibility ##\chi_e##. Calculate the force on a point charge ##q## situated a distance ##d## above the origin. Solution : The surface bound charge on the ##xy## plane is of opposite sign to ##q##, so the force will be...
Back
Top