def _define(self, name, shape='gaussian', sigma_params=None):
self.shape = shape
if name is None:
return
try:
elem, line = [w.title() for w in name.split()]
except:
return
if line == 'Ka': line = 'Ka1'
dat = xray_line(elem, line, _larch=self._larch)
if dat is not None:
ecenter = dat[0]
if self.center is None:
self.center = Parameter(name='center',
value=ecenter,
vary=False,
_larch=self._larch)
if sigma_params is not None:
if len(sigma_params) == 2 and self.sigma is None:
if isParameter(sigma_params[0]):
sigma_params = (sigma_params[0].name,
sigma_params[1].name)
expr = "%s + %s * %f" % (sigma_params[0], sigma_params[1],
ecenter)
self.sigma = Parameter(name='sigma',
expr=expr,
_larch=self._larch)
def _define(self, name, shape='gaussian', sigma_params=None):
self.shape = shape
if name is None:
return
try:
elem, line = [w.title() for w in name.split()]
except:
return
if line == 'Ka': line='Ka1'
dat = xray_line(elem, line, _larch=self._larch)
if dat is not None:
ecenter = dat[0]
if self.center is None:
self.center = Parameter(name='center',
value=ecenter,
vary=False,
_larch=self._larch)
if sigma_params is not None:
if len(sigma_params) == 2 and self.sigma is None:
if isParameter(sigma_params[0]):
sigma_params = (sigma_params[0].name,
sigma_params[1].name)
expr = "%s + %s * %f" % (sigma_params[0],
sigma_params[1],
ecenter)
self.sigma = Parameter(name='sigma',
expr=expr,
_larch=self._larch)
def fluo_corr(energy, mu, formula, elem, group=None, edge='K', anginp=45,
angout=45, _larch=None, **pre_kws):
"""correct over-absorption (self-absorption) for fluorescene XAFS
using the FLUO alogrithm of D. Haskel.
Arguments
---------
energy array of energies
mu uncorrected fluorescence mu
formula string for sample stoichiometry
elem atomic symbol or Z of absorbing element
group output group [default None]
edge name of edge ('K', 'L3', ...) [default 'K']
anginp input angle in degrees [default 45]
angout output angle in degrees [default 45]
Additional keywords will be passed to pre_edge(), which will be used
to ensure consistent normalization.
Returns
--------
None, writes `mu_corr` and `norm_corr` (normalized `mu_corr`)
to output group.
Notes
-----
Support First Argument Group convention, requiring group
members 'energy' and 'mu'
"""
energy, mu, group = parse_group_args(energy, members=('energy', 'mu'),
defaults=(mu,), group=group,
fcn_name='fluo_corr')
# generate normalized mu for correction
preinp = preedge(energy, mu, **pre_kws)
mu_inp = preinp['norm']
anginp = max(1.e-7, np.deg2rad(anginp))
angout = max(1.e-7, np.deg2rad(angout))
# find edge energies and fluorescence line energy
e_edge = xray_edge(elem, edge, _larch=_larch)[0]
e_fluor = xray_line(elem, edge, _larch=_larch)[0]
# calculate mu(E) for fluorescence energy, above, below edge
energies = np.array([e_fluor, e_edge-10.0, e_edge+10.0])
muvals = material_mu(formula, energies, density=1, _larch=_larch)
mu_fluor = muvals[0] * np.sin(anginp)/np.sin(angout)
mu_below = muvals[1]
mu_celem = muvals[2] - muvals[1]
alpha = (mu_fluor + mu_below)/mu_celem
mu_corr = mu_inp*alpha/(alpha + 1 - mu_inp)
preout = preedge(energy, mu_corr, **pre_kws)
if group is not None:
group = set_xafsGroup(group, _larch=_larch)
group.mu_corr = mu_corr
group.norm_corr = preout['norm']
def find_xray_line(z, edge):
"""
Finds most intense X-ray emission line energy for a given element and edge.
"""
intensity = 0
line = ''
for key, value in xray_lines(z).items() :
if value.initial_level == edge.upper():
if value.intensity > intensity:
intensity = value.intensity
line = key
return xray_line(z, line[:-1])
def xrf_calib_init_roi(mca, roiname):
"""initial calibration step for MCA:
find energy locations for one ROI
"""
if not isLarchMCAGroup(mca):
print( 'Not a valid MCA')
return
energy = 1.0*mca.energy
chans = 1.0*np.arange(len(energy))
counts = mca.counts
bgr = getattr(mca, 'bgr', None)
if bgr is not None:
counts = counts - bgr
if not hasattr(mca, 'init_calib'):
mca.init_calib = OrderedDict()
roi = None
for xroi in mca.rois:
if xroi.name == roiname:
roi = xroi
break
if roi is None:
return
words = roiname.split()
elem = words[0].title()
family = 'Ka'
if len(words) > 1:
family = words[1].title()
if family == 'Lb':
family = 'Lb1'
eknown = xray_line(elem, family)[0]/1000.0
llim = max(0, roi.left - roi.bgr_width)
hlim = min(len(chans)-1, roi.right + roi.bgr_width)
segcounts = counts[llim:hlim]
maxcounts = max(segcounts)
ccen = llim + np.where(segcounts==maxcounts)[0]
ecen = ccen * mca.slope + mca.offset
bkgcounts = counts[llim] + counts[hlim]
if maxcounts < 2*bkgcounts:
mca.init_calib[roiname] = (eknown, ecen, 0.0, ccen, None)
else:
model = GaussianModel() + ConstantModel()
params = model.make_params(amplitude=maxcounts,
sigma=(chans[hlim]-chans[llim])/2.0,
center=ccen-llim, c=0.00)
params['center'].min = -10
params['center'].max = hlim - llim + 10
params['c'].min = -10
out = model.fit(counts[llim:hlim], params, x=chans[llim:hlim])
ccen = llim + out.params['center'].value
ecen = ccen * mca.slope + mca.offset
fwhm = out.params['fwhm'].value * mca.slope
mca.init_calib[roiname] = (eknown, ecen, fwhm, ccen, out)
def xrf_calib_fitrois(mca, _larch=None):
"""initial calibration step for MCA:
find energy locations for all ROIs
"""
if not isLarchMCAGroup(mca):
print('Not a valid MCA')
return
energy = 1.0 * mca.energy
chans = 1.0 * np.arange(len(energy))
counts = mca.counts
bgr = getattr(mca, 'bgr', None)
if bgr is not None:
counts = counts - bgr
calib = OrderedDict()
for roi in mca.rois:
words = roi.name.split()
elem = words[0].title()
family = 'ka'
if len(words) > 1:
family = words[1]
try:
eknown = xray_line(elem, family, _larch=_larch)[0] / 1000.0
except:
continue
llim = max(0, roi.left - roi.bgr_width)
hlim = min(len(chans) - 1, roi.right + roi.bgr_width)
fit = fit_peak(chans[llim:hlim],
counts[llim:hlim],
'Gaussian',
background='constant',
_larch=_larch)
ccen = fit.params.center.value
ecen = ccen * mca.slope + mca.offset
fwhm = 2.354820 * fit.params.sigma.value * mca.slope
calib[roi.name] = (eknown, ecen, fwhm, ccen, fit)
mca.init_calib = calib
def xrf_calib_fitrois(mca, _larch=None):
"""initial calibration step for MCA:
find energy locations for all ROIs
"""
if not isLarchMCAGroup(mca):
print( 'Not a valid MCA')
return
energy = 1.0*mca.energy
chans = 1.0*np.arange(len(energy))
counts = mca.counts
bgr = getattr(mca, 'bgr', None)
if bgr is not None:
counts = counts - bgr
calib = OrderedDict()
for roi in mca.rois:
words = roi.name.split()
elem = words[0].title()
family = 'ka'
if len(words) > 1:
family = words[1]
try:
eknown = xray_line(elem, family, _larch=_larch)[0]/1000.0
except:
continue
llim = max(0, roi.left - roi.bgr_width)
hlim = min(len(chans)-1, roi.right + roi.bgr_width)
fit = fit_peak(chans[llim:hlim], counts[llim:hlim],
'Gaussian', background='constant',
_larch=_larch)
ccen = fit.params['center'].value
ecen = ccen * mca.slope + mca.offset
fwhm = 2.354820 * fit.params['sigma'].value * mca.slope
calib[roi.name] = (eknown, ecen, fwhm, ccen, fit)
mca.init_calib = calib
def mback(energy, mu, group=None, order=3, z=None, edge='K', e0=None, emin=None, emax=None,
whiteline=None, leexiang=False, tables='chantler', fit_erfc=False, return_f1=False,
_larch=None):
"""
Match mu(E) data for tabulated f''(E) using the MBACK algorithm and,
optionally, the Lee & Xiang extension
Arguments:
energy, mu: arrays of energy and mu(E)
order: order of polynomial [3]
group: output group (and input group for e0)
z: Z number of absorber
edge: absorption edge (K, L3)
e0: edge energy
emin: beginning energy for fit
emax: ending energy for fit
whiteline: exclusion zone around white lines
leexiang: flag to use the Lee & Xiang extension
tables: 'chantler' (default) or 'cl'
fit_erfc: True to float parameters of error function
return_f1: True to put the f1 array in the group
Returns:
group.f2: tabulated f2(E)
group.f1: tabulated f1(E) (if return_f1 is True)
group.fpp: matched data
group.mback_params: Group of parameters for the minimization
References:
* MBACK (Weng, Waldo, Penner-Hahn): http://dx.doi.org/10.1086/303711
* Lee and Xiang: http://dx.doi.org/10.1088/0004-637X/702/2/970
* Cromer-Liberman: http://dx.doi.org/10.1063/1.1674266
* Chantler: http://dx.doi.org/10.1063/1.555974
"""
order=int(order)
if order < 1: order = 1 # set order of polynomial
if order > MAXORDER: order = MAXORDER
### implement the First Argument Group convention
energy, mu, group = parse_group_args(energy, members=('energy', 'mu'),
defaults=(mu,), group=group,
fcn_name='mback')
if len(energy.shape) > 1:
energy = energy.squeeze()
if len(mu.shape) > 1:
mu = mu.squeeze()
group = set_xafsGroup(group, _larch=_larch)
if e0 is None: # need to run find_e0:
e0 = xray_edge(z, edge, _larch=_larch)[0]
if e0 is None:
e0 = group.e0
if e0 is None:
find_e0(energy, mu, group=group)
### theta is an array used to exclude the regions <emin, >emax, and
### around white lines, theta=0.0 in excluded regions, theta=1.0 elsewhere
(i1, i2) = (0, len(energy)-1)
if emin is not None: i1 = index_of(energy, emin)
if emax is not None: i2 = index_of(energy, emax)
theta = np.ones(len(energy)) # default: 1 throughout
theta[0:i1] = 0
theta[i2:-1] = 0
if whiteline:
pre = 1.0*(energy<e0)
post = 1.0*(energy>e0+float(whiteline))
theta = theta * (pre + post)
if edge.lower().startswith('l'):
l2 = xray_edge(z, 'L2', _larch=_larch)[0]
l2_pre = 1.0*(energy<l2)
l2_post = 1.0*(energy>l2+float(whiteline))
theta = theta * (l2_pre + l2_post)
## this is used to weight the pre- and post-edge differently as
## defined in the MBACK paper
weight1 = 1*(energy<e0)
weight2 = 1*(energy>e0)
weight = np.sqrt(sum(weight1))*weight1 + np.sqrt(sum(weight2))*weight2
## get the f'' function from CL or Chantler
if tables.lower() == 'chantler':
f1 = f1_chantler(z, energy, _larch=_larch)
f2 = f2_chantler(z, energy, _larch=_larch)
else:
(f1, f2) = f1f2(z, energy, edge=edge, _larch=_larch)
group.f2=f2
if return_f1: group.f1=f1
n = edge
if edge.lower().startswith('l'): n = 'L'
params = Group(s = Parameter(1, vary=True, _larch=_larch), # scale of data
xi = Parameter(50, vary=fit_erfc, min=0, _larch=_larch), # width of erfc
em = Parameter(xray_line(z, n, _larch=_larch)[0], vary=False, _larch=_larch), # erfc centroid
e0 = Parameter(e0, vary=False, _larch=_larch), # abs. edge energy
## various arrays need by the objective function
en = energy,
mu = mu,
f2 = group.f2,
weight = weight,
theta = theta,
leexiang = leexiang,
_larch = _larch)
if fit_erfc:
params.a = Parameter(1, vary=True, _larch=_larch) # amplitude of erfc
else:
params.a = Parameter(0, vary=False, _larch=_larch) # amplitude of erfc
for i in range(order): # polynomial coefficients
setattr(params, 'c%d' % i, Parameter(0, vary=True, _larch=_larch))
fit = Minimizer(match_f2, params, _larch=_larch, toler=1.e-5)
fit.leastsq()
eoff = energy - params.e0.value
normalization_function = params.a.value*erfc((energy-params.em.value)/params.xi.value) + params.c0.value
for i in range(MAXORDER):
j = i+1
attr = 'c%d' % j
if hasattr(params, attr):
normalization_function = normalization_function + getattr(getattr(params, attr), 'value') * eoff**j
group.fpp = params.s*mu - normalization_function
group.mback_params = params
def mback(energy,
mu,
group=None,
order=3,
z=None,
edge='K',
e0=None,
emin=None,
emax=None,
whiteline=None,
leexiang=False,
tables='chantler',
fit_erfc=False,
return_f1=False,
_larch=None):
"""
Match mu(E) data for tabulated f''(E) using the MBACK algorithm and,
optionally, the Lee & Xiang extension
Arguments:
energy, mu: arrays of energy and mu(E)
order: order of polynomial [3]
group: output group (and input group for e0)
z: Z number of absorber
edge: absorption edge (K, L3)
e0: edge energy
emin: beginning energy for fit
emax: ending energy for fit
whiteline: exclusion zone around white lines
leexiang: flag to use the Lee & Xiang extension
tables: 'chantler' (default) or 'cl'
fit_erfc: True to float parameters of error function
return_f1: True to put the f1 array in the group
Returns:
group.f2: tabulated f2(E)
group.f1: tabulated f1(E) (if return_f1 is True)
group.fpp: matched data
group.mback_params: Group of parameters for the minimization
References:
* MBACK (Weng, Waldo, Penner-Hahn): http://dx.doi.org/10.1086/303711
* Lee and Xiang: http://dx.doi.org/10.1088/0004-637X/702/2/970
* Cromer-Liberman: http://dx.doi.org/10.1063/1.1674266
* Chantler: http://dx.doi.org/10.1063/1.555974
"""
order = int(order)
if order < 1: order = 1 # set order of polynomial
if order > MAXORDER: order = MAXORDER
### implement the First Argument Group convention
energy, mu, group = parse_group_args(energy,
members=('energy', 'mu'),
defaults=(mu, ),
group=group,
fcn_name='mback')
if len(energy.shape) > 1:
energy = energy.squeeze()
if len(mu.shape) > 1:
mu = mu.squeeze()
group = set_xafsGroup(group, _larch=_larch)
if e0 is None: # need to run find_e0:
e0 = xray_edge(z, edge, _larch=_larch)[0]
if e0 is None:
e0 = group.e0
if e0 is None:
find_e0(energy, mu, group=group)
### theta is an array used to exclude the regions <emin, >emax, and
### around white lines, theta=0.0 in excluded regions, theta=1.0 elsewhere
(i1, i2) = (0, len(energy) - 1)
if emin is not None: i1 = index_of(energy, emin)
if emax is not None: i2 = index_of(energy, emax)
theta = np.ones(len(energy)) # default: 1 throughout
theta[0:i1] = 0
theta[i2:-1] = 0
if whiteline:
pre = 1.0 * (energy < e0)
post = 1.0 * (energy > e0 + float(whiteline))
theta = theta * (pre + post)
if edge.lower().startswith('l'):
l2 = xray_edge(z, 'L2', _larch=_larch)[0]
l2_pre = 1.0 * (energy < l2)
l2_post = 1.0 * (energy > l2 + float(whiteline))
theta = theta * (l2_pre + l2_post)
## this is used to weight the pre- and post-edge differently as
## defined in the MBACK paper
weight1 = 1 * (energy < e0)
weight2 = 1 * (energy > e0)
weight = np.sqrt(sum(weight1)) * weight1 + np.sqrt(sum(weight2)) * weight2
## get the f'' function from CL or Chantler
if tables.lower() == 'chantler':
f1 = f1_chantler(z, energy, _larch=_larch)
f2 = f2_chantler(z, energy, _larch=_larch)
else:
(f1, f2) = f1f2(z, energy, edge=edge, _larch=_larch)
group.f2 = f2
if return_f1: group.f1 = f1
n = edge
if edge.lower().startswith('l'): n = 'L'
params = Group(
s=Parameter(1, vary=True, _larch=_larch), # scale of data
xi=Parameter(50, vary=fit_erfc, min=0, _larch=_larch), # width of erfc
em=Parameter(xray_line(z, n, _larch=_larch)[0],
vary=False,
_larch=_larch), # erfc centroid
e0=Parameter(e0, vary=False, _larch=_larch), # abs. edge energy
## various arrays need by the objective function
en=energy,
mu=mu,
f2=group.f2,
weight=weight,
theta=theta,
leexiang=leexiang,
_larch=_larch)
if fit_erfc:
params.a = Parameter(1, vary=True, _larch=_larch) # amplitude of erfc
else:
params.a = Parameter(0, vary=False, _larch=_larch) # amplitude of erfc
for i in range(order): # polynomial coefficients
setattr(params, 'c%d' % i, Parameter(0, vary=True, _larch=_larch))
fit = Minimizer(match_f2, params, _larch=_larch, toler=1.e-5)
fit.leastsq()
eoff = energy - params.e0.value
normalization_function = params.a.value * erfc(
(energy - params.em.value) / params.xi.value) + params.c0.value
for i in range(MAXORDER):
j = i + 1
attr = 'c%d' % j
if hasattr(params, attr):
normalization_function = normalization_function + getattr(
getattr(params, attr), 'value') * eoff**j
group.fpp = params.s * mu - normalization_function
group.mback_params = params
def mback(energy,
mu=None,
group=None,
order=3,
z=None,
edge='K',
e0=None,
emin=None,
emax=None,
whiteline=None,
leexiang=False,
tables='chantler',
fit_erfc=False,
return_f1=False,
_larch=None):
"""
Match mu(E) data for tabulated f''(E) using the MBACK algorithm and,
optionally, the Lee & Xiang extension
Arguments:
energy, mu: arrays of energy and mu(E)
order: order of polynomial [3]
group: output group (and input group for e0)
z: Z number of absorber
edge: absorption edge (K, L3)
e0: edge energy
emin: beginning energy for fit
emax: ending energy for fit
whiteline: exclusion zone around white lines
leexiang: flag to use the Lee & Xiang extension
tables: 'chantler' (default) or 'cl'
fit_erfc: True to float parameters of error function
return_f1: True to put the f1 array in the group
Returns:
group.f2: tabulated f2(E)
group.f1: tabulated f1(E) (if return_f1 is True)
group.fpp: matched data
group.mback_params: Group of parameters for the minimization
References:
* MBACK (Weng, Waldo, Penner-Hahn): http://dx.doi.org/10.1086/303711
* Lee and Xiang: http://dx.doi.org/10.1088/0004-637X/702/2/970
* Cromer-Liberman: http://dx.doi.org/10.1063/1.1674266
* Chantler: http://dx.doi.org/10.1063/1.555974
"""
order = int(order)
if order < 1: order = 1 # set order of polynomial
if order > MAXORDER: order = MAXORDER
### implement the First Argument Group convention
energy, mu, group = parse_group_args(energy,
members=('energy', 'mu'),
defaults=(mu, ),
group=group,
fcn_name='mback')
if len(energy.shape) > 1:
energy = energy.squeeze()
if len(mu.shape) > 1:
mu = mu.squeeze()
group = set_xafsGroup(group, _larch=_larch)
if e0 is None: # need to run find_e0:
e0 = xray_edge(z, edge, _larch=_larch)[0]
if e0 is None:
e0 = group.e0
if e0 is None:
find_e0(energy, mu, group=group)
### theta is an array used to exclude the regions <emin, >emax, and
### around white lines, theta=0.0 in excluded regions, theta=1.0 elsewhere
(i1, i2) = (0, len(energy) - 1)
if emin is not None: i1 = index_of(energy, emin)
if emax is not None: i2 = index_of(energy, emax)
theta = np.ones(len(energy)) # default: 1 throughout
theta[0:i1] = 0
theta[i2:-1] = 0
if whiteline:
pre = 1.0 * (energy < e0)
post = 1.0 * (energy > e0 + float(whiteline))
theta = theta * (pre + post)
if edge.lower().startswith('l'):
l2 = xray_edge(z, 'L2', _larch=_larch)[0]
l2_pre = 1.0 * (energy < l2)
l2_post = 1.0 * (energy > l2 + float(whiteline))
theta = theta * (l2_pre + l2_post)
## this is used to weight the pre- and post-edge differently as
## defined in the MBACK paper
weight1 = 1 * (energy < e0)
weight2 = 1 * (energy > e0)
weight = np.sqrt(sum(weight1)) * weight1 + np.sqrt(sum(weight2)) * weight2
## get the f'' function from CL or Chantler
if tables.lower() == 'chantler':
f1 = f1_chantler(z, energy, _larch=_larch)
f2 = f2_chantler(z, energy, _larch=_larch)
else:
(f1, f2) = f1f2(z, energy, edge=edge, _larch=_larch)
group.f2 = f2
if return_f1:
group.f1 = f1
em = xray_line(z, edge.upper(), _larch=_larch)[0] # erfc centroid
params = Parameters()
params.add(name='s', value=1, vary=True) # scale of data
params.add(name='xi', value=50, vary=fit_erfc, min=0) # width of erfc
params.add(name='a', value=0, vary=False) # amplitude of erfc
if fit_erfc:
params['a'].value = 1
params['a'].vary = True
for i in range(order): # polynomial coefficients
params.add(name='c%d' % i, value=0, vary=True)
out = minimize(match_f2,
params,
method='leastsq',
gtol=1.e-5,
ftol=1.e-5,
xtol=1.e-5,
epsfcn=1.e-5,
kws=dict(en=energy,
mu=mu,
f2=f2,
e0=e0,
em=em,
order=order,
weight=weight,
theta=theta,
leexiang=leexiang))
opars = out.params.valuesdict()
eoff = energy - e0
norm_function = opars['a'] * erfc(
(energy - em) / opars['xi']) + opars['c0']
for i in range(order):
j = i + 1
attr = 'c%d' % j
if attr in opars:
norm_function += opars[attr] * eoff**j
group.e0 = e0
group.fpp = opars['s'] * mu - norm_function
group.mback_params = opars
tmp = Group(energy=energy, mu=group.f2 - norm_function, e0=0)
# calculate edge step from f2 + norm_function: should be very smooth
pre_f2 = preedge(energy, group.f2 + norm_function, e0=e0, nnorm=2, nvict=0)
group.edge_step = pre_f2['edge_step'] / opars['s']
pre_fpp = preedge(energy, mu, e0=e0, nnorm=2, nvict=0)
group.norm = (mu - pre_fpp['pre_edge']) / group.edge_step
def fluo_corr(energy,
mu,
formula,
elem,
group=None,
edge='K',
anginp=45,
angout=45,
_larch=None,
**pre_kws):
"""correct over-absorption (self-absorption) for fluorescene XAFS
using the FLUO alogrithm of D. Haskel.
Arguments
---------
energy array of energies
mu uncorrected fluorescence mu
formula string for sample stoichiometry
elem atomic symbol or Z of absorbing element
group output group [default None]
edge name of edge ('K', 'L3', ...) [default 'K']
anginp input angle in degrees [default 45]
angout output angle in degrees [default 45]
Additional keywords will be passed to pre_edge(), which will be used
to ensure consistent normalization.
Returns
--------
None, writes `mu_corr` and `norm_corr` (normalized `mu_corr`)
to output group.
Notes
-----
Support First Argument Group convention, requiring group
members 'energy' and 'mu'
"""
energy, mu, group = parse_group_args(energy,
members=('energy', 'mu'),
defaults=(mu, ),
group=group,
fcn_name='fluo_corr')
# generate normalized mu for correction
preinp = preedge(energy, mu, **pre_kws)
mu_inp = preinp['norm']
anginp = max(1.e-7, np.deg2rad(anginp))
angout = max(1.e-7, np.deg2rad(angout))
# find edge energies and fluorescence line energy
e_edge = xray_edge(elem, edge, _larch=_larch)[0]
e_fluor = xray_line(elem, edge, _larch=_larch)[0]
# calculate mu(E) for fluorescence energy, above, below edge
energies = np.array([e_fluor, e_edge - 10.0, e_edge + 10.0])
muvals = material_mu(formula, energies, density=1, _larch=_larch)
mu_fluor = muvals[0] * np.sin(anginp) / np.sin(angout)
mu_below = muvals[1]
mu_celem = muvals[2] - muvals[1]
alpha = (mu_fluor + mu_below) / mu_celem
mu_corr = mu_inp * alpha / (alpha + 1 - mu_inp)
preout = preedge(energy, mu_corr, **pre_kws)
if group is not None:
group = set_xafsGroup(group, _larch=_larch)
group.mu_corr = mu_corr
group.norm_corr = preout['norm']
