The electronic absorption spectrum of pyrazine crystals has been studied using single crystals at 4.2°K and polarized light. The origin shows three lines that are interpreted as (i) a , k = 0, factor group state at 26247.6 cm−1, (ii) two lines at 26254.7 and 26253.4 cm−1 corresponding to a split , factor group state. These interpretations are made on the basis of high‐field Zeeman effect studies. A low‐field Zeeman study has revealed the ordering of magnetic substates in each factor group level at . This yields the order for the free molecule. The zero‐field splitting is approximately + 0.3 cm−1 . A discussion of the relationship between such spin‐state ordering and the electronic structure of pyrazine in a state is also presented.
REFERENCES
1.
2.
3.
4.
5.
E. F. Zalewski, Jr., Ph.D. thesis, The University of Chicago, Chicago, Ill., June 1968.
6.
7.
8.
9.
R. H.
Clarke
and R. M.
Hochstrasser
, J. Chem. Phys.
47
, 1915
(1967
).10.
R. H.
Clarke
and R. M.
Hochstrasser
, J. Chem. Phys.
48
, 1745
(1968
).11.
These designations arc based on the phase definition Such a definition is very appropriate tor pyrazine since the b axis is a symmetry axis common to both twins. The plus and minus designations accordingly refer to symmetry or antisymmetry of the exciton states to the twofold interchange axis about b.
12.
The calculations were performed by A. Zewail and involved using the Fourier convolution method [see H. F. Hameka, Introduction to Quantum Theory (Harper and Row, New York, 1967), Appendix C]. The numerical results are significantly different from those of Sternlicht,13 but the ordering of the zero‐field states is not changed.
13.
14.
15.
16.
17.
K. K.
Innes
, J. P.
Byrne
, and J. G.
Ross
, J. Mol. Spectry.
22
, 125
(1967
).
This content is only available via PDF.
© 1970 American Institute of Physics.
1970
American Institute of Physics
You do not currently have access to this content.
