Photoionization studies of (H2O)2 and (HF)2 producing H3O+ and H2F+ yield 7.18±0.08 eV (165.8±1.8 kcal/mole) and 4.09±0.06 eV (94.3±1.4 kcal/mole) as the proton affinities of H2O and HF, respectively. The measured ionization potential of (H2O)2, 11.21±0.09 eV, along with the known ionization potential of H2O, 12.615±0.001 eV, allow the deduction of a lower bound for the dissociation energy of (H2O)2:1.58±0.13 eV (36±3 kcal/mole). The experiments have demonstrated that photoionization of dimers is one of the most useful general methods for the determination of proton affinities.

1.
R.
Yamdagni
and
P.
Kebarle
,
J. Am. Chem. Soc.
98
,
1320
(
1976
).
2.
C. Y.
Ng
,
B. H.
Mahan
, and
Y. T.
Lee
,
J. Chem. Phys.
65
,
1956
(
1976
);
C. Y. Ng, Ph.D. thesis, University of California, Berkeley, 1976.
3.
C. Y.
Ng
,
D. J.
Trevor
,
B. H.
Mahan
, and
Y. T.
Lee
,
J. Chem. Phys.
65
,
4327
(
1976
);
C. Y.
Ng
,
D. J.
Trevor
,
B. H.
Mahan
, and
Y. T.
Lee
,
J. Chem. Phys.
66
,
446
(
1977
).,
J. Chem. Phys.
4.
C. Y.
Ng
,
P. W.
Tiedemann
,
B. H.
Mahan
, and
Y. T.
Lee
,
J. Chem. Phys.
66
,
3385
(
1977
).
5.
L.
Karlsson
,
L.
Mattsson
,
R.
Jadrny
,
R. G.
Albridge
,
S.
Pinchas
,
T.
Bergmark
, and
K.
Siegbahn
,
J. Chem. Phys.
62
,
4745
(
1975
).
6.
To arrive at this number 4±1 kcal/mol has been used as the bond energy of water dimer at 0 °K, based on the following reported values: The study of infrared band intensities as a function of temperature gave a value of 3.8 kcal/mol;
W. P. Luck, in The Hydrogen Bond, Recent Developments in Theory and Experiments, edited by P. Schuster, G. Zundel, and C. Sandorfy (North‐Holland, New York, 1976) p. 1396. A value of 5.2±1.5 kcal/mol between 20–50 °C from submillimeter absorption of the dimer has been determined;
H. A.
Gebbie
,
W. J.
Burroughs
,
J.
Chamberlain
,
J. E.
Harries
, and
R. G.
Jones
,
Nature
221
,
143
(
1969
). Calculations of the second virial coefficient from theoretical potentials have bracketed the value between 3 and 4 kcal/mol;
C.
Braun
and
H.
Leidecker
,
J. Chem. Phys.
61
,
3104
(
1974
). Empirical potentials made to fit a variety of experimental parameters gave 3.5 kcal/mol;
L. L.
Shipman
and
H. A.
Scheraga
,
J. Chem. Phys.
78
,
909
(
1974
). Ab initio CI calculation gave a value of ∼5 kcal/mol;
G. H. F.
Diercksen
,
W. P.
Kraemer
, and
B. O.
Roos
,
Theor. Chim. Acta
36
,
249
(
1975
).
7.
M. Newton, private communication (Double ζ basis set).
8.
V. H.
Dibeler
,
J. A.
Walker
and
M.
Rosenstock
,
J. Res. Natl. Bur. Stand.
70A
,
459
(
1966
).
9.
W. A. Chupka, Chemical Spectroscopy and Photochemistry in the Vacuum Ultraviolet, edited by C. Sandorfy, P. J. Ausloos, and M. B. Robin (D. Reidel, Holland, 1974), p. 443.
10.
K. E.
McCulloh
,
Int. J. Mass Spectrom. Ion Phys.
21
,
333
(
1976
).
11.
JANAF Thermochemical Tables, Natl. Stand. Ref. Data Ser. 37, Natl. Bur. Stand., June 1971.
12.
R. J.
Cotter
and
W. S.
Koski
,
J. Chem. Phys.
59
,
784
(
1973
).
13.
J.
Long
and
B.
Munson
,
J. Am. Chem. Soc.
95
,
2427
(
1973
).
14.
S.
Chong
,
R. A.
Myers
, Jr.
, and
J. L.
Franklin
,
J. Chem. Phys.
56
,
2427
(
1972
).
15.
J. L.
Beauchamp
and
S. E.
Buttrill
, Jr.
,
J. Chem. Phys.
48
,
1783
(
1968
).
16.
P. A.
Kollman
,
C. F.
Bender
,
Chem. Phys. Lett.
21
,
271
(
1973
).
17.
J.
Berkowitz
,
W. A.
Chupka
,
P. M.
Guyon
,
J. H.
Holloway
, and
R.
Spohr
,
J. Chem. Phys.
54
,
5165
(
1971
).
18.
G. C. Pimentel, A. L. McClellan, The Hydrogen Bond (W. H. Freeman, San Francisco, 1960), p. 211f.
19.
J. L.
Beauchamp
,
Ann. Rev. Phys. Chem.
22
,
527
(
1971
).
20.
P.
Schuster
,
Theor. Chim. Acta
19
,
212
(
1970
).
21.
A. C.
Hopkinson
,
N. K.
Holbrook
,
K.
Yates
, and
I. G.
Csizmadia
,
J. Chem. Phys.
49
,
3596
(
1968
).
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