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ionization potentials

lower and upper bound for each shell is given as follows:
iplow = OpacPoint.ipElement[0][ns][nion][nelem];
iphi = OpacPoint.ipElement[1][ns][nion][nelem];

for entire species,
Heavy.ipHeavy[nion][nelem]

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solar default abundances
set in zeroabund

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shells
Shell.chShell[0], "1s" etc

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strings giving labels

shell labels stored in Shell.chShell[]

set in zerologic.c

elementnames.h has names
#include "elementnames.h"
elementnames.chElementSym has 2ch name as used in label
elementnames.chElementNameShort[nelem] is 4-char name in caps
elementnames.chElementName has full name upper and lower case

ReadElement will look for element on line

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Abundances and ionic fractions
xIonFracs[2][1]
 * first argument is ionization stage, 
 * 1 for atom, 2 for first ion
 * 0 is total abundance all species
 *
 * second argument is atomic number minus 1, so H is 0

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limits to species

upper and lower limits to range of element, nelem is on the C scale,
but IonLow and IonHigh are physical, 1 to N+1 where N is the atomic number.

IonRange.IonLow[nelem]
IonRange.IonHigh[nelem]

IonRange is initally set in nsset to 1 for IonLow, and IonHigh to ipZ+2 where
ipZ is on the C scale.

if the element is turned off, both are set to -1

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turning element off

if the element is turned off, both 
IonRange.IonLow[nelem]
IonRange.IonHigh[nelem]
are set to -1

element turned off, check 
#include "elmton.h"
if( elmton.lgElmtOn[ipZ] )

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mass in atomic mass units
AtomcWgt.AtomicWeight[i]
set in zerologic, about 1 for H, 4 for he, etc