Subject: CCL: Summary: History of atomic shell labels

From: Mikael Johansson <mpjohans(at)pcu.helsinki.fi>
Date: Mon, 2 Jun 2003 17:07:06 +0300 (EEST)

Hello All!

The recent discussion on orbitals reminded me that I never posted a
summary on a few questions I posed two years ago. As it's some time ago,
and I didn't get an answer for everything, here comes the questions
again. The summary part is further below:

1.) Who came up with the idea of starting labeling of the atomic shells
    from K, L, M..., and more interestingly; why start from K?
2.) The subshell labels came from the spectral lines of alkali metals, but
    where Sharp, Principal and Diffuse lines are quite self explanatory,
    I have some difficulty of picturing a "Fundamental" spectral line :-)
    Any help?
3.) Was there a good reason for leaving out j from the labels for
    subshells?

So far I've managed to get a definitive answer on the origin of K,
L, M, etc., which was introduced by Barkla, 'K' coming from German
"K|rzere Wellenldngen" and 'L' from "Ldngere Wellenldngen".

This was suggested by Eric Scerri (see below) and I also found it in a
book by V. Trkal, Electronic Structure of Atoms and Molecules (1969).

j was apparently left out just to avoid confusion. No definitive answer on
that though.

No-one has had any idea of the origin of the "fundamental" spectral line.

Below is a list of the replies I've got. The book by Trkal was recommended
to me by Dr. Henrik Konschin of our lab.

Have a nice day,
    Mikael J.
    http://www.helsinki.fi/~mpjohans/
=====================================

From: Steve Williams

[...]

>3.) Was there a good reason for leaving out j from the labels for
>     subshells?

The story I have heard about this is that since j and J are used both as
general angular momentum quantum number symbols, as well as for total
(spin
+ orbital) angular momentum, it was thought too likely to cause confusion
if j and J were used as orbital angular momentum symbols as well.

Good luck with your search...
Steve Williams
ASU Chemistry
Boone, NC 28608 USA

========================================
From: Eric Scerri

[...]

(1)  The historical origin of K, L, M etc dates back to the work of
the British X-ray spectroscopist George Barkla who was later awarded
a Nobel Prize.
If I recall his key article was in 1911 in the Philosophical Magazine.

He is mentioned in all standard historical accounts such as the books
by Pais for example.  Title: Inner Bound.

It was his work which led to van den Broek's suggestion that the
ordering principle for the periodic system might be atomic number
rather than atomic weight which in turn inspired Moseley to
experimentally verify this idea in 1914.

van den Broek also cited Geiger and Marsden's famous experiements on
the scattering of alpha radiation.

More about all these episodes appears in my forthcoming book on the
Story of the Periodic System to be published by McGraw-Hill as a
'trade book'.

(2)  no idea!

(3)  Presumably because j or even J is used for the vectorial sum of
l and s and L and S respectively.  Having an orbital labeled j would
just confuse matters.

regards,
-- 

Dr. Eric Scerri ,
UCLA,
Department of Chemistry & Biochemistry,
607 Charles E. Young Drive East,
Los Angeles,  CA 90095-1569
USA

========================================

From: Michael Nolan

Hi,

I can answer number 1 for you:

K = kurz
L = lang
and after that it's alphabetical.
kurz is german for short
lang is german for long.

The early spectroscopists were german!

regards
Mick

[...]

-- 
********************************************************
Michael Nolan
Computational Modelling, NMRC
Lee Maltings, Prospect Row, Cork, IRELAND

========================================

From: Huub van Dam

[...]

> 3.) Was there a good reason for leaving out j from the labels for
>     subshells?

I would think it was thought that j could be mistaken for being an i too
easily. However, I have authorative information on this one.

[...]

--

========================================================================

Huub van Dam                               E-mail:
CCLRC Daresbury Laboratory                  phone: +44-1925-603362
Daresbury, Warrington                         fax: +44-1925-603634
Cheshire, UK
WA4 4AD

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