We show that a supersonic molecular beam source will significantly improve the quality of molecular photoelectron spectra by reducing both Doppler and rotational broadening of the target gas, and that the benefits of such a source are realized for spectrometers operating at resolutions of ?20 meV. The photoelectron spectra of the O2+2Πg,v′=0+e←O23Σg transition in molecular oxygen and the C2H4+2B3u +eC2H41Ag transition in ethylene are presented as examples of the technique. Newly resolved vibrational structure in the ethylene spectrum is compared to recent theoretical calculations and to the vibrational structure of the 3s Rydberg transition at 1744 Å.

1.
P. M.
Dehmer
and
J. L.
Dehmer
,
J. Chem. Phys.
68
,
3462
(
1978
).
2.
P. M.
Dehmer
and
J. L.
Dehmer
,
J. Chem. Phys.
69
,
125
(
1978
).
3.
A. D.
Baker
,
C.
Baker
,
C. R.
Brundle
, and
D. W.
Turner
,
Int. J. Mass Spectrosc. Ion Phys.
1
,
285
(
1968
).
4.
G. R.
Branton
,
D. C.
Frost
,
T.
Makita
,
C. A.
McDowell
, and
I. A.
Stenhouse
,
J. Chem. Phys.
52
,
802
(
1970
).
5.
C. R.
Brundle
and
D. B.
Brown
,
Spectrochim. Acta A
27
,
2491
(
1971
).
6.
R.
Stockbauer
and
M. G.
Inghram
,
J. Electron Spectrosc.
7
,
492
(
1974
).
7.
A. J.
Merer
and
L.
Schoonveld
,
Can. J. Phys.
47
,
1731
(
1969
).
8.
F. H.
Watson
, Jr.
and
M. W.
Nycum
,
Spectrosc. Lett.
8
,
223
(
1975
).
9.
J. A. R.
Samson
and
J. L.
Gardner
,
Can. J. Phys.
53
,
1948
(
1975
).
10.
C. E.
Kuyatt
and
J. Arol
Simpson
,
Rev. Sci. Instrum.
38
,
103
(
1967
).
11.
J. A. R.
Samson
,
Rev. Sci. Instrum.
40
,
1174
(
1969
).
12.
G. Herzberg, Spectra of Diatomic Molecules (Van Nostrand, Princeton, New Jersey, 1950), pp. 125–128 and pp. 204–209. In the present work ν4 is assumed to be a constant for all the rotational lines in the band (where ν is the energy of a given rotational transition).
13.
J. L. Dehmer, Argonne National Laboratory Radiological and Environmental Research Division Annual Report, July 1974–June 1975, ANL‐75‐60, Part I, pp. 61–63.
14.
J. L.
Dehmer
and
D.
Dill
,
Phys. Rev. A
18
,
164
(
1978
).
15.
R. E.
Smalley
,
L.
Wharton
, and
D. H.
Levy
,
J. Chem. Phys.
63
,
4977
(
1975
).
16.
J. B.
Anderson
and
J. B.
Fenn
,
Phys. Fluids
8
,
780
(
1965
).
17.
H. Ashkenas and F. S. Sherman, Rarefied Gas Dynamics, Fourth Symposium, Vol. II, J. H. Deleeuw, Ed., (Academic, New York, 1966), pp. 84–105.
18.
R. Campargue, Symposium on Relaxation Methods in Relation to Molecular Structure (Academic, New York, 1966), pp. 287–296.
19.
J. O. Hirschfelder, C. F. Curtiss, and R. B. Bird, Molecular Theory of Gases and Liquids (Wiley, New York, 1954), Table I‐A, pp. 1110–1113.
20.
Using the present nozzle design, the mole fraction of clusters is only a few percent even at very high nozzle stagnation pressures, as was determined in the work on the rare gases discussed in Refs. 1 and 2.
21.
An excellent review of work on the ultraviolet spectrum of ethylene to 1968 is given by
A. J.
Merer
and
R. S.
Mulliken
,
Chem. Rev.
69
,
639
(
1969
).
22.
For a discussion of the selection rules for electronic and vibronic transitions see (a) G. Herzberg, Electronic Spectra and Electronic Structure of Polyatomic Molecules (Van Nostrand, New York, 1966), Chapter II,
and (b)
H.
Sponer
and
E.
Teller
,
Rev. Mod. Phys.
13
,
75
(
1941
).
23.
P. D.
Foo
and
K. K.
Innes
,
J. Chem. Phys.
60
,
4582
(
1974
).
24.
S. D.
Peyerimhoff
and
R. J.
Buenker
,
Theoret. Chim. Acta
27
,
243
(
1972
).
25.
H.
Köppel
,
W.
Domcke
,
L. S.
Cederbaum
, and
W.
von Niessen
,
J. Chem. Phys.
69
,
4252
(
1978
).
26.
F. H.
Watson
, Jr.
,
A. T.
Armstrong
, and
S. P.
McGlynn
,
Theoret. Chim. Acta
16
,
75
(
1970
).
27.
In the discussion of ethylene vibrations, Watson and Nycum use G. Herzberg’s notation to assign the normal modes, but use R. S. Mulliken’s suggested reference frame to determine the symmetries of the vibrations. See (a) G. Herzberg, Infrared and Raman Spectra (Van Nostrand Reinhold, New York, 1945), pp. 106–108,
and (b)
R. S.
Mulliken
,
J. Chem. Phys.
23
,
1997
(
1955
). The correspondence between the two systems is given in the Appendix of this paper.
28.
L. E.
McMurchie
and
E. R.
Davidson
,
J. Chem. Phys.
66
,
2959
(
1977
);
L. E.
McMurchie
and
E. R.
Davidson
,
67
,
5613
(
1977
).,
J. Chem. Phys.
29.
P. G.
Wilkinson
and
R. S.
Mulliken
,
J. Chem. Phys.
23
,
1895
(
1955
).
This content is only available via PDF.
You do not currently have access to this content.