///|
pub let elementary_charge : Double = 1.602176634e-19

///|
pub let electron_mass : Double = 9.1093837139e-31

///|
pub let proton_mass : Double = 1.67262192595e-27

///|
pub let vacuum_permittivity : Double = 8.8541878188e-12

///|
pub let boltzmann_constant : Double = 1.380649e-23

///|
pub let pi : Double = 3.141592653589793

///|
pub fn thermal_velocity(temperature_k : Double, mass_kg~ : Double) -> Double {
  (boltzmann_constant * temperature_k / mass_kg).sqrt()
}

///|
pub fn electron_thermal_velocity(temperature_k : Double) -> Double {
  thermal_velocity(temperature_k, mass_kg=electron_mass)
}