Mostly atomic and some molecular data for analytic stellar spectroscopy
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( Mostly) Atomic and (Some ) Molecular Data for Analytic Stellar Spectroscopy. Charles R. Cowley: U. Michigan Saul J. Adelman: The Citadel Donald J. Bord: UM Dearborn. Lots of help from many others!!. Outline of Talk. Ionization Energies for neutrals and first four ions.

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Mostly atomic and some molecular data for analytic stellar spectroscopy

(Mostly) Atomic and (Some ) Molecular Data for AnalyticStellar Spectroscopy

Charles R. Cowley: U. Michigan

Saul J. Adelman: The Citadel

Donald J. Bord: UM Dearborn

Lots of help from many others!!

Outline of Talk

  • Ionization Energies for neutrals and first

  • four ions.

2. Atomic Data Bases

3. Partition functions

4. Opacity: photoionization cross sections; TopBase

Part 1: Ionization Energies

Visit our website:

Or, a number of others for more general info:


Part 2: Atomic Data

For Atomic Data, conveniently arranged for

spectral synthesis, two primary sources:

There may be other instances in the history of

science where so many have owed so much to

so few, but I don’t know of them.

Both of these sites are under continuous


Generally speaking: Either of these sources will

provide the basis for an encouraging synthesis

of atomic features in most stars.

Details are another matter. Even within small wavelength intervals,

of 5 to 10 A, there are generally a few features for which one cannot

find an appropriate atomic line, even by modifying the oscillator

strength by an order of magnitude or more.

This is typical in a region with molecular features, when using VALD,

which has not (as of May 2002) yet included molecules.

But it is also common in other regions, and very probably due to

incompleteness of atomic data: Either the lines are not in the

data bases, or the oscillator strengths are egregiously in error.

Here is a rather shocking plot comparing VALD

and Kurucz-site log(gf)’s for Fe I

Standard deviation: 0.86

Standard error: 0.05

The big differences are all for “second-generation

lines,” lines not in the Multiplet Tables. So they are

not lines typically studied.

However, they are all from classifies levels, and

would appear in any spectrum synthesis.

Generally speaking, one might prefer VALD for

elements heavier than the iron peak.

Changes in the Kurucz data beyond what is on

the CDRoms (and therefore in VALD) are mostly

for the important spectra of Fe I and Fe II.

This was the situation when I browsed the

Kurucz site at the end of March 2002, and it

it subject to change.

We have choices other than just RLK

or VALD.

Check the NIST site, and hunt around among the

links. An E-book is nearing completion, which

will contain much useful information on the first

two spectra of elements from H to Es. There will

be wavelengths for some 11,000 lines, but gf’s

for only about 2500 lines.

A NIST project that is just beginning will have much more extensive data, including gf’s and hfs.

Of course, any improvements by NIST should be

incorporated in VALD and Kurucz data bases!

The Main Problem is PERSON Power

Snooping on the internet can bring up a wealth

of relevant information.

Here are just a few examples of places from which

one can get useful data:

Be advised that sometimes, one must get a

reference, and then pull up the journal electronically.

Here is an incomplete example of what one can find.

Part 3: Partition functions

Focus on two aspects of partition functions:

1. Completeness of low levels.

2. Treatment of levels above those known



Various algorithms are in use to give the

partition function u(T). Undoubtedly some

are better than others. All must be based

on data that is sufficiently complete.

Partition functions are important, algorithms

less so.

Recent examples:

Added levels from

Cowan code, or

laboratory work.

REE III (1994)

Ho II, W, Os


Mostly the changes are

small—a few per cent,

except in cases where

ranks were D, E, or

missing altogether.

For Ho II, nearly 50%:

worth making!

Following a little-known study by Van’t Veer-Menneret

(CR, 253, 380, 1961), we assert that the contribution

to the partition function from levels above those

typically known, ARE NOT IMPORTANT for the cal-

culation of line strengths.

It is easy to see this in a simple case. We consider

the situation where the dominant ion is the first—

virtually all atoms are first ionized. But, we are

to compute a line arising from the first (neutral)


We assert that in general, the partition function

for the atom or ion (i) is unimportant for the

line strength if the element is predominantly

(i+1)-th fold ionized.

It is easy to see from the previous slide that this

must be approximately the case, but the assertion

covers a lot of parameter space, and should be

checked for special cases.

Part 4: Photoionization cross sections

“Opacity of opacity, saith the Preacher, opacity

of opacity; all is opacity.”

Ecclesiastes –

From a recently translated Agnostic gospel.

Continuum 

Red level interacts

with continuum

First ionization limit

These lines

are in Kurucz


Solid line: TopBase

Dotted: Hydrogenic





(H and K)


It is straightforward to smooth these TopBase

cross sections without changing the net absorption.

This has been done by a number of people, and

systematically by Prieto (2002).

The next step, already being carried out, is to

parameterize the smoothed fits for use in opacity

routines, such as si1op, al1op, fe1op, etc. used

in the Atlas codes. These routines give what I

call the “K-factor”:

Ca I 4s4d 1D

Epilog: Molecular Spectra, et al.

Best overall site: New TiO, H2O

RadEn Database:



Atomic and Molecular Data and software: