def read_ionization_energies( element ):
"""
Read the ionization energies from a data file
Parameters
----------
element: string
The atomic symbol of the considered ionizable species
(e.g. 'He', 'N' ; do not use 'Helium' or 'Nitrogen')
Returns
-------
An array with one array element per ionization state, containing the
ionization energy in Joules.
"""
# Open and read the file atomic_data.txt
filename = os.path.join( os.path.dirname(__file__), 'atomic_data.txt' )
with open(filename) as f:
text_data = f.read()
# Parse the data using regular expressions (a.k.a. regex)
# (see https://docs.python.org/2/library/re.html)
# The regex command below parses lines of the type
# '\n 10 | Ne IV | +3 | [97.1900]'
# and only considers those for which the element (Ne in the above example)
# matches the element which is passed as argument of this function
# For each line that satisfies this requirement, it extracts a tuple with
# - the atomic number (represented as (\d+))
# - the ionization level (represented as the second (\d+))
# - the ionization energy (represented as (\d+\.*\d*))
regex_command = \
'\n\s+(\d+)\s+\|\s+%s\s+\w+\s+\|\s+\+*(\d+)\s+\|\s+\(*\[*(\d+\.*\d*)' \
%element
list_of_tuples = re.findall( regex_command, text_data )
# Return None if the requested element was not found
if list_of_tuples == []:
return(None)
# Go through the list of tuples and fill the array of ionization energies.
atomic_number = int( list_of_tuples[0][0] )
assert atomic_number > 0
energies = np.zeros( atomic_number )
for ion_level in range( atomic_number ):
# Check that, when reading the file,
# we obtained the correct ionization level
assert ion_level == int( list_of_tuples[ion_level][1] )
# Get the ionization energy and convert in Joules using e
energies[ ion_level ] = e * float( list_of_tuples[ion_level][2] )
return( energies )
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