invnm_to_mrad.py

import numpy as np
from scipy.constants import electron_mass, elementary_charge, c, hbar, h

def relativistic_wavelength(kV=300):
    "Returns relativistic wavelength in meters"
    V = 1e3 * kV
    top = h * c
    bottom = np.sqrt(
        elementary_charge * V * (2 * electron_mass * c ** 2 + elementary_charge * V)
    )
    wavelength = top / bottom
    return wavelength
  
def invnm_to_mrad(k, kV=300):
    """Converts reciprocal nm units to mrad units
    """
    wavelength = relativistic_wavelength(kV)
    k = k * 1 / (1e-9)
    theta = np.arctan(k * wavelength)
    return theta * 1000