Primary radical yields of hydrated electrons, H atoms, and OH radicals are determined by measuring hydrated electron formation following a 4 microsecond pulse of X rays. The pH dependence of free radical yields beyond pH 12 is determined by observation of the hydrated electrons

Fielden, E. M.

Hart, E. J.

English

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June 1969	 Brief 69-10167 
•	 AEC-NASA TECH BRIEF 
AEC-NASA Tech Briefs describe innovations resulting from the research and development program 
of the U.S. AEC or from AEC-NASA interagency efforts. They are issued to encourage commercial 
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the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Primary Radical Yields in Pulse Irradiated Alkaline Aqueous Solution 
The	 relative	 primary	 radical	 yields	 of	 hydrated placed on an absolute basis by measuring the manga-
electrons, H atoms and OH radicals have been deter- nate ion yield in a formate-permanganate solution. 
mined by measuring the amount of hydrated electron G(eq) is 2.7 in neutral and 3.1 in strong alkaline 
formed	 following	 a	 single	 4-isec	 pulse, of	 X-rays. solutions.	 The	 primary	 radical	 yields	 g(eq),	 g(H) 
Renewed	 interest	 in	 measuring	 free	 radical	 and and g(OH), computed from diffusion theory, are 3.04, 
molecular	 product	 yields	 of	 ionizing	 radiations	 in 0.53	 and	 2.81,	 respectively, 	 at	 pH	 13	 and	 g(eq) 
alkaline solutions has resulted from the discovery of equals 2.65 at pH 7. There was essentially no differ-
the hydrated electron, eãq.
	
Recent papers have es- ence in the sum G(eq) + G(H) + G(OH) in the pH 
tablished	 that	 in	 addition	 to	 primary	 eq	 yield, range from 12 to 14. 
g(eq),	 there	 is	 a	 primary	 H-atom	 yield, g(H),	 in Notes: 
neutral and alkaline solutions. However, beyond a pH 1. The report, "Primary Radical Yields in Pulse Irradi-
of 12, particularly conflicting results are obtained. The ated Alkaline Aqueous Solution," Radiation Re-
problem of measuring primary radical yields in alka- search, 32, No. 3, pp. 564-580 (1967) includes a 
line solutions above pH 12 is aggravated by the mci- detailed description of methods used and results. 
dence	 of	 chain	 reactions;	 by	 the	 ionization	 of the Additional information is available in "A Unique 
hydroxyl radical and of hydrogen peroxide; and by New Ion - The Hydrated Electron," Argonne 
carbonate	 ion,	 a	 common	 impurity	 and	 hydroxyl Reviews, Vol. 1, No. 4, October 1964. 
radical scavenger. 2.	 Inquiries concerning this report may be directed 
To resolve the question of free radical yields be- to: 
yond	 pH	 12,	 the	 pH	 dependence	 of g(eq)	 was Office of Industrial Cooperation 
determined	 by direct observation of e q	 developed Argonne National Laboratory 
by a pulse of X-rays. The optical density of an irradi- 9700 South Cass Avenue 
ated solution was measured at 7000A under carefully Argonne, Illinois 60439 
controlled conditions. Reference: B69-10167 
In neutral solution, the amount of hydrated electron Source: E. M. Fielden and E. J. Hart 
produced	 corresponds	 to	 G(eiq), and at	 high	 pH Chemistry Division 
values an additional amount is formed corresponding (ARG-10322) 
to G(H) by the reaction H + 0H	 = H 2 0 + eq. 
In the presence of dissolved hydrogen, the OH radical Patent status: 
in yield G(OH) is also converted to hydrated electrons Inquiries concerning rights for commercial use of 
by reaction with hydrogen. The high optical absorp- this innovation may be made to: 
tion of the hydrated electron at 7000A is used as a Mr. George H. Lee, Chief 
measure of its concentration. A pH range from 7 to Chicago Patent Group 
14.5 is covered. U.S. Atomic Energy Commission 
Above pH	 12, the total radical yield, G(eq) 	 + Chicago Operations Office 
G(H)	 + G(OH), is constant as is the total reducing 9800 South Cass Avenue 
yield,	 G(eq)	 +	 G(H).	 These	 relative	 yields	 are Argonne, Illinois 60439 	 Category 02
This document was prepared under the sponsorship of the Atomic liability resulting from the use of the information contained in this 
Energy Commission and/or the National Aeronautics and Space document, or warrants that the use of any information, apparatus, 
Administration. Neither the United States Government nor any per- method, or process disclosed in this document may not infringe pri-
son acting on behalf of the United States Government assumes any vately owned rights. 
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Primary radical yields in pulse irradiated alkaline aqueous solution

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