February 14, 1961

Or. P. 0'B. Montgomery
Department of Pathology
The University of Texas
Southwestern Medical School
5323 Harry Hines Boulevard
Dallas 35, Texas

Bear Doctor Montgomery:

A few days ago | had a very Interesting discussion with some people
from Philco In which some details of the UV-emitting CRO tube came out.
This Is plainly a very interesting source for many purposes.

During the past few months, we have been spending some time In
looking for suitable filters that might be used In connection with UV
microscopy. From our own experience, | suspect that you are rather
exasperated with what Is currently avaliable by way of Interference filters.
However, Mrs. Jane Sanders here has been able to effect some Improvements
in the lodine filter originally described by Hoshino and Yoshida and |
wonder If you would not find these advantageous for removing the undesirable
long wave length components In the output of the Philco tube. Possibly you
are already well acquainted with this type of filter but on the chance
that this Is not the case, | am taking the liberty of sending one along
together with the corresponding transmission spectra. The filter, as we
are using It In connection with low pressure mercury sources for the
isolation of the 2537 R line, consists of two parts: A) a methacyl film
cast on # quartz plate and containing the material cation xX, This [s
used here primarily to obliterate the window at around 330 R. 8) Is an
jodine-methacy! film also on quartz which gives a useful cut-off at about
370 mi. The two filters have been placed face to face and taped together;
C Is the transmission curve of the composite as we would use It.

These filters would be of material assistance to you, we will be happy
to send you more detaiis on their preparation. On the other hand, If you
are already well acquainted with them or If they do you no particular good
then Just toss them out.

| would be Interested to know if your findings on the L-2116 tube
agree in practice with the specifications given by the company or whether
there are departures from It, particularly with age during the useful life
of the tube. In addition, 1 wonder If you would be able to advise whether
It Is wiser to purchase such a tube without warranty at $750 or with
warranty for an additional 250.

Yours sincerely,

Joshue Lederberg
Professor of Genetics.

50 hark 3
copped