qpms/constants.py

   1 """
   2 Constants and unit conversion, mostly for standalode usage.
   3
   4 Previously, QPMS used scipy.constants in the python parts.
   5 Now the relevant ones are set explicitly here in order
   6 to avoid dependency on the whole scipy (which needs a fortran
   7 compiler to build.
   8
   9 The values are taken from scipy / "2018 CODATA recommended values".
  10 They slightly differ from the constants in GSL that are used
  11 in the C code. It would be desirable to use the same source,
  12 hence the values here might be subject to change in future versions.
  13 """
  14
  15 epsilon_0 = ε_0 = 8.8541878128e-12  # ± 0.0000000013e-12      F m^-1
  16 c = speed_of_light = 299792458.
  17 eV = e = elementary_charge = 1.602176487e-19  # ± 0000000040e-19    C
  18 hbar = ℏ = 1.054571800e-34  #  ± 0.000000013e-34    J s
  19 mu_0 = μ_0 = 1.25663706212e-6  #  ± 0.00000000019 e-6     N A^-2
  20
  21 from math import pi
  22 π = pi
  23
  24 μm = 1e-6
  25 nm = 1e-9
  26 # "SCUFF FREQUENCY UNIT"
  27 SU = 3e14
  28 SCUFF_OMEGAUNIT = SU
  29
  30 #freqs = freqs_weirdunits * c / μm
  31
  32 def nm2eV(lambda_nm, n = 1):
  33     return 2*π*c/(n * lambda_nm * nm) / (eV / ℏ)
  34
  35 def eV2nm(e_eV, n = 1):
  36     return 2*π*c/(n * e_eV * (eV/ℏ)) / nm
  37
  38 def SU2eV(e_SU):
  39     '''
  40     Scuff frequency units to eV.
  41     '''
  42     return e_SU * SU / (eV / ℏ)
  43
  44 def eV2SU(e_eV):
  45     return e_eV * (eV / ℏ) / SU
  46
  47 def SU2nm(e_SU, n = 1):
  48     return 2*π*c/(n * e_SU * SU) / nm
  49
  50 def nm2SU(lambda_nm, n = 1):
  51     return 2*π*c/(n * lambda_nm * nm) / SU
  52