PCRmagRedfield.py

# Mantid Repository : https://github.com/mantidproject/mantid
#
# Copyright © 2019 ISIS Rutherford Appleton Laboratory UKRI,
#   NScD Oak Ridge National Laboratory, European Spallation Source,
#   Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
# SPDX - License - Identifier: GPL - 3.0 +
# pylint: disable=invalid-name, anomalous-backslash-in-string, attribute-defined-outside-init

from mantid.api import IFunction1D, FunctionFactory
import numpy as np


class PCRmagRedfield(IFunction1D):

    def category(self):
        return "Muon\\MuonSpecific"

    def init(self):
        self.declareParameter("A0", 0.2, 'Amplitude')
        self.declareParameter("Delta", 0.2)
        self.declareParameter("Nu", 0.2)

    def function1D(self, x):
        A0 = self.getParameterValue("A0")
        Delta = self.getParameterValue("Delta")
        Nu = self.getParameterValue("Nu")
        W = 2 * np.pi * Delta
        Q = (Nu ** 2 + Delta ** 2) * Nu
        if Q > 0:
            Lambda = Delta ** 4 / Q
        else:
            Lambda = 0
        return A0 * (1./3 + 2./3 * np.exp(- Lambda * x) * np.cos(W * x))


FunctionFactory.subscribe(PCRmagRedfield)