#!/usr/bin/python
"""
A database like file containing numerical values of various natural constants
in SI units. Alphabetically ordered by name (not by variable name).
"""
# Constants
#==============================================================================
# Avogadro constant [1]
N_A = 6.022e23
# Bohr's Magneton [J/T]
mu_bohr = 9.274009994e-24
# Bohr radius [m]
a0 = 5.2917721067e-11
# Boltzmann constant [J/K]
k_B = 1.38064852e-23
# Dielectric constant in vacuum [C / V / m]
eps0 = 8.854e-12
# Electronvolt [J]
eV = 1.6021766208e-19
# Electron mass [kg]
m_e = 9.10938356e-31
# Planck's constant [J * s]
h = 6.626070040e-34
# Speed of light [m / s]
c = 299792458.
# Universal Gas constant [J / K / mol]
R = 8.3144598
# Dependent constants
#==============================================================================
# Electronvolt-nanometer conversion for light; 1239.84197
eV_nm_conversion = h*c/eV*1e9
# Utilities
#==============================================================================
[docs]def convert_eV_nm(eV_or_nm) :
"""
Convert between electronvolt and nanometers for electromagnetic waves.
The conversion follows from E = h*c/lambda and is simply::
nm_or_eV = 1239.84193 / eV_or_nm
**Parameters**
======== ==================================================================
eV_or_nm float; value in electronvolts or nanometers to be converted.
======== ==================================================================
**Returns**
======== ==================================================================
nm_or_eV float; if eV were given, this is the corresponding value in
nanometers, or vice versa.
======== ==================================================================
"""
nm_or_eV = eV_nm_conversion / eV_or_nm
return nm_or_eV