Richard Clark wrote:
On Sun, 11 Mar 2007 21:23:28 +0000, Ian White GM3SEK
wrote:

Richard cited the following as a claimed exception:

A photon is emitted in the cM band when an electron orbiting a
Hydrogen atom flips its magnetic pole. This event is vastly below the
short wavelengths you describe by a million-fold. A good number of
correspondents here are fully capable of detecting this event with
commercial gear already suitable for the Ham market. They could have
done it 50 years ago too.

That is an example of a quantum effect determining the *frequency* of an
RF emission... but the origin of the RF energy doesn't change its
character. If a signal generator is tuned to that frequency, it will
produce exactly the same kind of RF energy - a torrent of quanta so tiny
that their individual existence is irrelevant.

Hi Ian

Determining the *frequency*? That has to be the most obscure
contribution I've ever seen.

No, it's the simplest. A couple of days ago, I quoted and explained the
most basic equation of quantum mechanics:

E = hf

It means that whenever there is a transition between two energy levels,
a photon is emitted whose frequency is uniquely determined by the
difference between those energy levels.

The case you quoted was the so-called "hydrogen line". A hydrogen atom
can have the spin of its single electron aligned in the same direction
as that of its single proton; or in the opposite direction. The former
state has slightly more energy, and when the spin of one atom flips to
the lower-energy state, one quantum of EM radiation is emitted. The
frequency of that radiation is determined by the difference in energy
levels between the two states, and is 1.42GHz.

The hydrogen line is like any other spectral line, except that the
difference in energy levels is unusually small (optical spectroscopists
would call it "hyperfine splitting") so the energy comes out as
microwaves rather than light.

The point I was making was that 1.42GHz radiation generated in this
particular manner has no special properties other than its frequency. It
is exactly the same kind of RF energy as you'd get from a signal
generator tuned to the same frequency.



--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek