content: import 'math.dart';
  
  /// physical constants
  /// ##
  /// Reference:
  /// 1. https://physics.nist.gov/cuu/Constants/
  
  /// speed of light in vacuum
  const c = 299792458;
  const speedOfLight = c;
  
  const mu0 = 4e-7 * pi;
  
  const epsilon0 = 1 / (mu0 * c * c);
  
  /// Planck constant
  const h = 6.62607015e-34;
  const Planck = h;
  
  const hbar = h / (2 * pi);
  
  /// Newtonian constant of gravitation
  const G = 6.67430e-11;
  const gravitationalConstant = G;
  
  /// Standard acceleration of gravity
  const g = 9.80665;
  
  /// elementary charge
  const eC = 1.602176634e-19;
  const elementaryCharge = eC;
  
  /// molar gas constant
  const R = 8.314462618;
  const gasConstant = R;
  
  /// fine-structure constant
  const alpha = 7.2973525693e-3;
  const fineStructure = alpha;
  
  /// Avogadro constant
  const NA = 6.02214076e23;
  const Avogadro = NA;
  
  /// Boltzmann constant
  const k = 1.380649e23;
  const Boltzmann = k;
  
  /// Stefan-Boltzmann constant
  const sigma = 5.670374419e-8;
  const Stefan_Boltzmann = sigma;
  
  /// Wien wavelength displacement law constant
  const Wien = 2.897771955e-3;
  
  /// Rydberg constant
  const Rydberg = 10973731.568160;
  