TY - JOUR
T1 - Quantum yield and electron-transfer reaction of the lowest excited state of uranyl ion
AU - Rosenfeld-Grünwald, T.
AU - Rabani, J.
PY - 1980
Y1 - 1980
N2 - The pulsed photoreduction (using N2 laser photolysis technique) of uranyl ion, UO22+, both in its ground state and in the lowest excited state (at pH 2 and in 2 M H3PO4 aqueous solutions) has been studied. We found that *UO22+ is quenched by ruthenium tris(bipyridine) ions, Ru(bpy)32+, and Ru(bpy)33+ is formed; namely, *UO22+ is an electron-acceptor species. It is shown here that the rate of decay of *UO22+ in the presence of Ru(bpy)32+ exactly corresponds to the formation rate of Ru(bpy)33+, as measured by the bleaching of the Ru(bpy)32+ ground-state absorption. The excited state of Ru(bpy)32+ is found to be quenched by UO22+, and again Ru(bpy)33+ is formed, UO22+ being an electron acceptor in its ground state. The quantum yield of the formation of the lowest excited state of UO22+, φ*UO22+, multiplied by the yield of electron transfer, φetRu→*U, between *UO22+ and Ru(bpy)32+ is found to be 0.5 at pH 2 and unity in 2 M H3PO4 solution. In the presence of a negatively charged polyelectrolyte, such as poly(vinyl sulfate), PVS, the value of this product is reduced to an upper limit of 0.1. It is shown that φ*UO22+ is unaffected by the presence of PVS. The back reaction, UO2+ + Ru(bpy)33+ → UO22+ + Ru(bpy)32+, is a second-order reaction, k/ε (λ = 450 nm) = 1.05 × 105 s-1 cm at pH 2 and 1.78 × 102 s-1 cm in 2 M H3PO4 solution. This reaction is accelerated in the presence of O2 or PVS. The yields and rates of formations and reactions of the photochemical products are discussed.
AB - The pulsed photoreduction (using N2 laser photolysis technique) of uranyl ion, UO22+, both in its ground state and in the lowest excited state (at pH 2 and in 2 M H3PO4 aqueous solutions) has been studied. We found that *UO22+ is quenched by ruthenium tris(bipyridine) ions, Ru(bpy)32+, and Ru(bpy)33+ is formed; namely, *UO22+ is an electron-acceptor species. It is shown here that the rate of decay of *UO22+ in the presence of Ru(bpy)32+ exactly corresponds to the formation rate of Ru(bpy)33+, as measured by the bleaching of the Ru(bpy)32+ ground-state absorption. The excited state of Ru(bpy)32+ is found to be quenched by UO22+, and again Ru(bpy)33+ is formed, UO22+ being an electron acceptor in its ground state. The quantum yield of the formation of the lowest excited state of UO22+, φ*UO22+, multiplied by the yield of electron transfer, φetRu→*U, between *UO22+ and Ru(bpy)32+ is found to be 0.5 at pH 2 and unity in 2 M H3PO4 solution. In the presence of a negatively charged polyelectrolyte, such as poly(vinyl sulfate), PVS, the value of this product is reduced to an upper limit of 0.1. It is shown that φ*UO22+ is unaffected by the presence of PVS. The back reaction, UO2+ + Ru(bpy)33+ → UO22+ + Ru(bpy)32+, is a second-order reaction, k/ε (λ = 450 nm) = 1.05 × 105 s-1 cm at pH 2 and 1.78 × 102 s-1 cm in 2 M H3PO4 solution. This reaction is accelerated in the presence of O2 or PVS. The yields and rates of formations and reactions of the photochemical products are discussed.
UR - http://www.scopus.com/inward/record.url?scp=0039050755&partnerID=8YFLogxK
U2 - 10.1021/j100459a028
DO - 10.1021/j100459a028
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AN - SCOPUS:0039050755
SN - 0022-3654
VL - 84
SP - 2981
EP - 2985
JO - Journal of Physical Chemistry
JF - Journal of Physical Chemistry
IS - 22
ER -