COMMUNICATIONS TO THE. EDITOR
along with those containing Pu(II1) and Pu(1V) for comparison. These spectra were obtained with a solution 0.0089 M in total plutonium species in a 3.8cm. absorption cell at 400') using a Cary 14 H spectrophotometer. Spectrum A of Pu(1II) was obtained by
0.3
4219
-
11
predominantly plutonyl(IV), by sparging with 33% 0 2 in Clz; when the reaction was complete, spectrum cc1 was obtained. Removal of Cla from the solution by sparging with He resulted in diminution of the plutonyl(VI) and growth of the plutonyl(V) peaks and eventually in the precipitation of a portion of the plutonium as PuOz. This behavior is attributed to shifts in the equilibria PuO2Clz
=
PUOZCl
0.6 0.5
0.4 0.3 0.2
0.1 w
m
1.0
p:
0
m
=
Spectrum D, which is predominantly that of plutonyl(V), was obtained shortly before precipitation began. The behavior of the plutonyl species under various conditions was studied spectrophotometrically. The ratio of plutonyl(V) to plutonyl(V1) in Oz-Clz sparged solutions was found to vary inversely with the square root of the concentration of Clzin the sparge gas. With a given 02-Clz composition, the ratio increases with temperature and also depends on the composition of the solution, being greater in LiC1-KC1 eutectic than in LiC1-CsCl eutectic. In solutions sparged only with Clz, reduction of the plutonyl species to Pu(1II) and Pu(1V) occurs. This reduction proceeds quite slowly at low temperature. Sparging with HCl results in rapid reduction of the plutonyl species, initially to Pu(IV), then to Pu(II1).
0.7
u z c
+ '/ZClZ PUOZ + '/ZCl,
PUOZCl
0.9
U
0.8 0.7
0.6
HANFORD LABORATORIES J. L. SWANSON HANFORD ATOMICPRODUCTS OPERATION GENERALELECTRIC COMPANY RICHLAND, WASHINGTON RECEIVEDDECEMBER 6, 1963
0.5 0.4
0.3 0.2
0.1
On the Delayed Fluorescence of Pyrene Solutions. A Correction 0.5
1.0
1.5
2.0
2.5,
WAVELENGTH, M I C R O N S
Figure 1. Absorption spectra of Pu ions in LiCl-CsCl eutectic a t 400". A is Pu(III), B is Pu(IV), C is predominantly plutonyl(VI), and D is predominantly plutonyl(V).
dissolving PuCl3 in the eutectic and sparging with 2% H, in HCI to assure the absence of Pu(1V) Spectrum B of Pu(1V) was obtained by sparging with Clz to oxidize the Pu(I11) to Pu(1V); the spectrum indicates that a t least 910% of the plutonium was oxidized. The plutonium was then oxidized to plutonyl species,
Sir: The rate parameters describing the prompt and delayed fluorescence of pyrene in ethanol have been evaluatedl from experimental data on the spectra2 and on k , and ICID, the rate parameters of the monomer and excimer fluorescence, respectively, for pyrene in cy~lohexane.~In this analysis no correction was applied to allow for the difference in the refractive index n of cyclohexane (n = 1.43) and ethanol (n = (1) (2)
J. B. Birks, J . I'hys. Chem., 67, 2199 (1963). C. A. Parker and C. G. Hatchard, Trans. Faraday Soc., 59, 284 (1963).
(3)
J. B. Birks, D. J. Dyson, and I. H. Munro, Proc. Roy. (London), A275, 676 (1963).
Soc.
Volume 68, Number 9 February, 1964
COMMUKICATIOX~ TQ THE EDITOR
440
1.36) and its influence on the values of k,=.M and kfD. The analysis has now been repeated, taking4kf proportional to n2, and bhe following revised values for the rate parameters of pyrene in ethanol are obtained: k f M = 0.136 X lo7 set.-'; k,, = 1.05 X lo7 set.-'; lcD,M = 6 X lo9 1. mole-1 sec.-l; k , , = 0.073 X lo7 set.-'; IC,, = 0.86 X lo7 sec.-l; k,, = 0.83 X l o 7 sec.-l; q.l.i = 0.65, q D = 0.55, and ch = 5 X M , as In the previous analysis,' but values of a = 1.94 and 01 = 2.02 (instead of a = 1.45 and a = 1.52) are obtained from K z and Ka, respectively. It thus appears
The Journal of Physical Chemistry
that the triplet-triplet quenching results in the initial formation of excimers and excited monomers in the ratio of 2 : 1 , respectively, and not in the ratio 1.5:l as originally estimated. ~~~
(4)
~
~
~~
J. B. Birks and D. J. Dyson, Proc Rou. Soc (London), A275, 136 (1963)
THEP H Y S I C A L L A B O R A T O R I E S CNIVERSITY OF MANCHESTER JfAXCHESTER
13, E N G L 4 N D
RECEIVED DECEMBER 21, 1963
J . B. BIRES
