Ions and ion traps

[dtvmcdonald]

The thread has drifted! But still, I will say this! I teach,
sometimes (I'm retired, but come back to help) a lab course
in Chemistry for Juniors/Seniors. I've now done this for
40 years. This is Physical Chemistry Lab.

Experiments have changed, a bit, in those 40 years. There is much
more optics and much less mixing chemicals. We no longer, for example,
have them measure thermochemistry with wet methods or battery voltages
(i.e. "electrochemical potentials" ... an experiment in which, I should add,
the good students could get 4 significant figures right, and I could get 5,
with equipment made in the 1920s.) But they still do unwatered down
experiments, and learn as much fundamental stuff. And learn MORE about
setting up experiments. For example, they have to put together all the
lenses and the laser for a Raman experiment. This is not easy if you've
never done it. I can do it in five minutes. The students are lucky if they
can get it all done in three hours, the first time around.

But the toughest thing they have to learn is how to use an oscilloscope!
We have several experiments where they need to do this. One uses a simple
low frequency analog scope, one uses a low-end Tektronix 60 MHz digital
scope, and one uses the very fanciest of the fancy 1GHz high end Tektronix
digital ones (and needs all that GHz using the cutest little TO-5 can
photomultiplier you've ever seen ... a photomultiplier in a transistor can!)
The TA's have trouble learning to use scopes! I have trouble using
the fancy one and I've used these since they first came out ... you folks
probably have never had the "pleasure" of one of these in a totally unknown
state ... that's what "factory reset" is for.

But they learn a LOT. The old stuff, the new stuff. I really feel that
all this talk about students learning more in the old days is bunk. For
example ... they still use one analog scope.

And in fact thinking about one experiment was why I started this topic ...
we have a mass spec in the lab that does negative ions, and
except for F- and Cl-, which won't be in the gas in a CRT, they
are hard mostly quite hard to make. O- and OH- exist but generally
come from water, which also won't survive the getter in a tube.
The most likely molecules in a tube are H2 and CO, both of which
ooze out of iron and steel forever, and don't getter well on
the usual Barium getter (they do on Ti, but tubes don't use that.)
So the most likely negative ion in a CRT is H-. At least that's
my first guess. I wonder what it does to the phosphors to ruin them?

Doug McDonald