180
TABLE 66.
Pouarization In Heavy MIneRaL OIL ar —4 + 1°C
Band edge,
mu
Compound
3. p-Bis(2-(5-phenyloxazolyl)]benzene
(“POPOP’’)
6. 4,4’-Di(undecyloxy“-1)-1,1’-binaph-
395
360
thyl
7, 9,12-Di(n-oetadecyloxy }benz[e]-
440
acephenanthrylene
Upperline: A,myu
Lowerline: polarization (P), %
375
+43
350
360
+43
240
340
+43
330
320
+42
320
32k
+26
310
300
+11
300
+41
+38
+25
+33
+33
+82
410
395
375
355
340
320
800
+32
+32
+28
+24
+13
+11
+17
300
+31
290
+20»
310
—15
300
—19
390
370
+45
340
+45
300
+43
9. Tetraphenyl ethylene
380
350
+41
330
+38
310
+35
430
11. Trans-1-(4-biphenylyl) -2-(1-
390
12. Trans-1-(4-biphenyly})-2-pheny]-
365
13. 1,3,6,8-Tetraphenylpyrene
425
naphthyl) -ethylene
ethylene
+32¢)
+41
8. Dipheny!stilbene
10. 1,8-Diphenyl-1,3,5,7-octatetraene
290
+5
290
400
+41
380
+44
350
378
+40
365
+45
335
360
+40
350
+44
325
345
+41
335
+44
305
330
+38
320
+43
290
300
+26
305
+40
290
+42
+43
+43
+42
+439
400
+42
380
+41
370
+40
350
+35
330
+28
320
+18
()} or butyloxy or octyloxy.
6) at 290 mu, absorption bythe solvent is appreciable (A = 0.3). Whetherthis affects the result is conjectural.
Theory shows that if no depolarization takes place
flow directly into the chamber, now flowsfirst through
sion is (a) +50% when absorbing and emitting os-
the chamber into temperature equilibrium with the
gas in the chamber. Rapid temperature fluctua-
between absorption and emission, and if there is no
mixing of types, the degree of polarization P of emis-
cillators are parallel, and (b)
—3344% when per-
pendicular to each other. If there is overlap, the result
will be somewhere between the two extremes. De-
polarization (the result of rotation during the lifetime of the excited state), of course, reduces the
(absolute) value of the polarization, but its effect is
easily distinguished from that being discussed. De-
polarization affects the whole absorption spectrum,
whereas the effect being discussed is a function of
wavelength.
A principal difficulty encountered originally, es-
pecially as it affected the viscosity-effect study,
was temperature instability. Through modifications
of the apparatus, improved, though not completely
satisfactory, temperature control has been obtained.
A hollow jacket, thermally insulated on the outside, was added surrounding the cell chamber. The
jacket, filled with an antifreeze solution, has in it
also copper tubing coiled around the chamber. The
cold nitrogen gas, which originally was allowed to
the copper tubing in the jacket before entering the
chamber, thus tending to bring the surroundings of
tions in the chamber have been eliminated, but the
aim of holding the temperature invariant has not
been realized. It was thought that creation of slush
in the jacket would assure constancy; however, it was
found that even then there is a temperature gradient
in the jacket. The possibility of using more effective
insulation is being investigated.
A distinct improvement has been made in connec-
tion with the solvent used. A heavier mineral oil
has been obtained (Fisher Paraffin Oil 0-120),
of Saybolt 335/350, and an unexpected bonus has been
its transparency. Because of the improvement in the
latter, the range in which meaningful results can be
obtained has been extended downwards to about
290 mp. The absorbance of this oil in the 1-cm cell
does not reach 1.0 until 285 mp. The increased viscosity has lessened the depolarization so that higher
values of polarization are now realized. The limita-