M2L9e.txt

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For number of years, people pursued
measurements of the Lamb Shift with higher and higher
accuracy.
I just like the last sentence here.
This is now the next paper by Willis Lamb and Retherford.
And they are sort of saying that they wanted to measure the Lamb
Shift with higher precision, but then they
said the program was large and encountered
unexpected difficulties which required much more time
to surmount.
As a result, the paper promised two years ago was delayed.
I think this applies to many, many papers to be written,
but here the authors even say that up front it
took us two years longer to do the research than they
initially anticipated.
You see now the growing accuracy.
We have the Lamb Shift, which was
on the order of thousand megacycles, one gigahertz,
and the precision is now in the hundred kilohertz range.
This was the technology of the original discovery.
Then there was a next generation of experiments
on the Lamb Shift using separated oscillatory fields,
Ramsey techniques.
We'll talk about that later in the course.
And with these techniques, the accuracy of the Lamb Shift
is now in the one digit further in the 10 kilohertz regime.
There is a nice feature that we'll also discuss it later
that it was possible to obtain a linewidth
which is sub natural.
We talk about it that it's possible to do spectroscopy
on unstable states, which provides a linewidth narrower
than the natural linewidths.
If you want to get one sentence, but as an appetizer,
you just look at the atoms, which have not
decayed for a long time.
And if you play some tricks you can then
get a linewidth, which is several lifetime, which corresponds
to several lifetimes, and not just to the 1/e lifetime.
But there are some conditions that have to be met,
and those authors used it here to advantage
to narrow the line for the measurement of the Lamb Shift.
Yes?
So the abstract says that the result is not
in good agreement with theory.
What was the theoretical-- how far had it--
I don't know.
I don't know it at this point.
I will later give you comparison with theory
which is highly accurate.
So this was more some-- I assume at this point-- I'm not sure
if it was an experimental difficulty.
I didn't trace down what they meant in the abstract.

So these are the same authors, just a few years later.
The agreement between theory and experiment
is at the 2 standard deviation.
So I think this problem disappeared.
And I don't know if it was a fault of theory or experiment.