Electronic to vibration‐rotational‐translational energy transfer in the quenching of Na(3 2P3/2) by CO has been studied with state of the art crossed atomic, molecular, and laser beam techniques at 0.16 eV initial kinetic energy, and by ab initio CI calculations for the potential energy surfaces involved in the process. Double differential quenching cross sections are measured as a function of scattering angle and energy transferred to the molecule. A pronounced structure in the energy transfer spectra as well as a partial backward scattering is attributed to two different mechanisms, a ’’direct’’ one and one which proceeds through ’’complex’’ formation. The observations are explained by the calculated potential energy surfaces (PES) for the first excited states Ã 2A′(Ã′ 2A″) and the ground state X̃ 2A′ which exhibit two crossing seams below the 2.1 eV excitation energy: (i) one for colinear approach of Na* on the carbon side of CO with its lowest energy 1.06 eV at Rc(Na–CO)= 5.5a0, rc(C–O) = 2.35a0 responsible for the direct process and (ii) one for colinear approach of Na* on the oxygen end of CO with 1.28 eV at Rc= 4.9a0 and rc= 2.47a0, allowing the quenching after ’’complex’’ formation. The angularly integrated cross sections are maximal (27 Å2/eV) at an energy transferred to the molecule equivalent to five vibrational quanta. Comparison with bulk data suggests strong rotational excitation (two vibrational quanta in the average) as can be rationalized from the anisotropy of the X̃ 2A′ PES near the crossing region. Total quenching cross sections and their temperature dependence can be explained by the absorbing sphere model using the calculated location and energy of the crossing seams.

1.
For recent reviews see, e.g., (a)
S.
Lemont
and
G. W.
Flynn
,
Annu. Rev. Phys. Chem.
28
,
261
(
1977
);
(b) J. T. Yardley, Introduction to Molecular Energy Transfer (Academio, New York, 1980);
(c) I. V. Hertel, in The Excited State in Chemical Physics, edited by J. W. McGowan (Wiley, London, 1981), p. 341; (d) H. W. Breckenridge and H. Umemoto, in Dynarnics of the Excited State, edited by K. P. Lawley (Wiley, London, 1982);
(e) I. V. Hertel, ibid. p. 475.
2.
H. S. Y.
Hsu
and
M. C.
Lin
,
Chem. Phys. Lett.
42
,
78
(
1976
);
J. Chem. Phys.
73
,
2188
(
1980
).
3.
J. A.
Silver
,
N. C.
Blais
, and
G. H.
Kwei
,
J. Chem. Phys.
67
,
839
(
1977
);
J. A.
Silver
,
N. C.
Blais
, and
G. H.
Kwei
,
71
,
3412
(
1979
).,
J. Chem. Phys.
4.
(a)
I. V.
Hertel
,
H.
Hofmann
, and
K. A.
Rost
,
J. Chem. Phys.
71
,
674
(
1979
);
(b)
W.
Reiland
,
H.‐U.
Tittes
, and
I. V.
Hertel
,
Phys. Rev. Lett.
48
,
1389
(
1982
);
(c) W. Reiland, C.‐P. Schulz, H.‐U. Tittes, and I. V. Hertel, Chem. Phys. Lett. (in press).
5.
(a)
P.
Habitz
,
Chem. Phys.
54
,
131
(
1980
);
(b) D. Papierowska, V. Bonacic‐Koutecký, W. Reiland, and I. V. Hertel, (to be published).
6.
P.
Botschwina
,
W.
Meyer
,
I. V.
Hertel
, and
W.
Reiland
,
J. Chem. Phys.
75
,
5438
(
1981
).
7.
C. H.
Becker
and
R. P.
Saxon
,
J. Chem. Phys.
75
,
4899
(
1981
).
8.
J. C.
Tully
and
R. K.
Preston
,
J. Chem. Phys.
55
,
562
(
1971
).
9.
P.
McGuire
and
J. C.
Bellum
,
J. Chem. Phys.
71
,
1975
(
1979
).
10.
P. Archiel and P. Habitz (to be published).
11.
P. Botschwina and W. Meyer (to be published).
12.
E.
Bauer
,
E. R.
Fisher
, and
F. R.
Gilmore
,
J. Chem. Phys.
51
,
4173
(
1969
).
13.
E. A.
Gislason
,
A. W.
Kleyn
, and
J.
Los
,
Chem. Phys.
59
,
91
(
1981
).
14.
M. M.
Hubers
,
A. W.
Kleyn
, and
J.
Los
,
Chem. Phys.
17
,
3031
(
1976
).
15.
(a)
C.
Bottcher
and
C. V.
Sukumar
,
J. Phys. B
10
,
2853
(
1977
);
(b)
H. S.
Taylor
,
Chem. Phys. Lett.
64
,
117
(
1979
).
16.
J. R.
Barker
and
R. E.
Weston
, Jr.
,
J. Chem. Phys.
65
,
1427
(
1976
).
17.
In C2v geometry these states have B2 and A1 symmetry and the crossings are allowed.
18.
(a)
I. V.
Hertel
,
H.
Hofmann
, and
K. A.
Rost
,
Phys. Rev. Lett.
38
,
343
(
1977
);
(b) W. Reiland, G. Jamieson, H.‐U. Tittes, and I. V. Hertel, Z. Phys. A (in press).
19.
R. B.
Bernstein
and
R. D.
Levine
,
Adv. At. Mol. Phys.
11
,
215
(
1975
).
20.
Hsu and Lin measured at temperatures between 486 and 672 K without observing a significant change in the CO vibrational distribution. We evaluate their 672 K data (〈Ec.m.〉 = 0.06 eV) which is closest to our Ec.m = 0.16 eV.
21.
(a)
R. J.
Buenker
,
S. D.
Peyerimhoff
, and
W. E.
Kammer
,
J. Chem. Phys.
55
,
814
(
1971
);
(b)
R. J.
Buenker
and
S. D.
Peyerimhoff
,
Chem. Phys.
9
,
75
(
1975
).
22.
B. O.
Roos
and
P.
Siegbahn
,
Theor. Chim. Acta
17
,
209
(
1970
).
23.
V.
Steammler
,
Chem. Phys.
17
,
187
(
1976
).
24.
(a)
R. J.
Buenker
and
S. D.
Peyerimhoff
,
Theor. Chim. Acta
35
,
33
(
1974
);
(b)
R. J.
Buenker
,
S. D.
Peyerimhoff
, and
W.
Butscher
,
Mol. Phys.
35
,
771
(
1978
).
25.
G. Herzberg, Spectra of Diatnmic Molecules, 2nd ed. (Von Nostrand Reinhold, New York, 1950).
26.
M.
Zubek
and
C.
Szmytkowski
,
J. Phys. B
10
,
L27
(
1977
).
27.
We note that for application of the picture of a ball rolling on the PES’s, the r and R coordinates in Figs. 8 and 12 have to be scaled as q1 = a1/2r and q1 = b1/2.R, with a and b being the reduced mass of the C‐O and of the Na‐CO system, respectively. In this way, one would obtain a valley, very narrow in the r coordinate, while in the contrary, we have expanded the r scale for better visibility. The skewing angle for the r and R coordinates as defined here is 90° and the kinetic energy is 12/2+q̇22/2.
28.
G. E.
Zahr
,
R. K.
Preston
, and
W. H.
Miller
,
J. Chem. Phys.
62
,
1127
(
1975
).
This content is only available via PDF.
You do not currently have access to this content.