Cary®
NEWS
Details are available from Dr. W. W. Brandt, Kansas State University, Manhattan, Kansas.
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A center for the collection and evaluation of data on atomic transition probabilities and cross sections has been established at the National Bureau of Standards. The center will compile atomic data in areas where experimental or theoretical investigations are being conducted at NBS. This compilation has been started as part of a research program, sponsored by the Office of Naval Research and the Advanced Research Projects Agency, which seeks to supply the data needed for current and future research in plasma physics and astrophysics. In order that the data center may be as effective and up to date as possible, authors are urged to send preprints and reprints of pertinent publications to the Atomic Physics Data Center, Far West Building, National Bureau of Standards, Washington 25, D. C.
NSF Grants Recent grants by the National Science Foundation will assist college and secondary school science teachers and undergraduate science students. NSF has granted $700,000 for 1961 to 41 educational institutions for research participation programs for 350 college science teachers. The corresponding program for 310 high school teachers will cost $618,000. Most of the work will be done during the summer. The college teacher program requires Circle No. 24 on Readers' Service Card
Radiant energy of wavelengths othei than those defined by the indicate! wavelength and slit width.
RANGE 1-2 Abs4j>0-1 Abs.
WET ABSORBANCE READINGS 1.81 + 4.3! -=6.
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Absorbante Values of A t tenuatdrs t e h u a t i r s J1 35 I .(Total V a l u t = 4.35 f !.I
CARY MODEL 14 Serial 412
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Scan: 2.5 A / s e c .
• 1 .05
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slit widths, tn\n
-d~ .χ 2200
NBS Establishes Atomic Data Center
Evaluating Spectrophotometer Performance
STRAY LIGHT:
Foreign Grants U. S. Government grants available for university lecturing and advanced research abroad are described in several new booklets. These grants are made available under the Fulbright and Smith-Mundt Acts. The publications available include a general information booklet and specific ones describing grants available from Latin America, South and Southeast Asia, and Australia and New Zealand. Copies are available from the Conference Board of Associated Research Councils, Committee on International Exchange of Persons, 2101 Constitution Ave., Washington 25, D. C.
NO.4
DATA S E R I E S
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2400
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2497-i- - 2 ! S O i r ~ 2 5 1 3 - * 2 S 2 3 1 2 5 3 4 1 25501 25781 2500™ flf&nts at which attenuatorcrwere added
Stray light of Cary M o d e l 14 is l e s s than 0 . 0 0 0 1 % over m u c h of r a n g e , 0.1% e v e n a t r a n g e l i m i t s . When spectrophotometers a r e operated close to t h e limits of their wavelength range, measurements are restricted by a combination of weak radiation from t h e source a n d / or poor detector sensitivity. In any spectral range, similar problems may be caused by absorbing solvents or use of t h e differential tech nique. Under these conditions, stray light lowers performance because it contributes a disproportionate amount to t h e total energy being measured. Also, t h e important advantages offered by high absorbance measurements —reduced errors due to contamination of cell windows, uncertainties in path length, etc.—can only be had if stray light is minimized. F o r these reasons, t h e Cary Model 14 has been designed with a double monochromator so t h a t stray light is extremely low. Measure ments with excellent accuracy can be made over t h e entire spectral range of t h e instrument. The spectrum illustrates one of t h e performance tests used in t h e manufacture of the Cary Model 14. A sample with sharp cut-off was scanned slowly toward shorter wavelengths, where its transmission is negligible. Calibrated optical attenuators were added, at t h e points indi cated, to t h e reference beam to extend t h e absorbance range. A false plateau or peak is found above 6.0 absorbance (.0001 %Ί). I t is caused by stray light, which amounts to less than 1 ppm. Stray light is just one of several important criteria on which spectro photometer performance should be based. Others include: Resolution, photometric ac curacy and reproducibility ; wavelength accu 1 jgjjgg racy and reproducibility. Because t h e Model 14 excels in each of these performance cri I.teria, many r e g a r d it as t h e finest instru ' ~~v>—' ment of its kind available. F o r additional " ' i l ' l || information w r i t e for Data File A24-61. I
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Cary®
INSTRUMENTS
APPLIED PHYSICS CORPORATION 2 7 2 4 South Peck
Road
Monrovia, California
