Missing levels lead to additional lines: the influence of nuclear spin statistics on femtosecond degenerate four wave mixing spectroscopy of polyatomic systems.
We present the results of comprehensive experimental and theoretical studies of the effect of nuclear spin statistics on the structure of rotational recurrences in femtosecond degenerate four-wave mixing (fs DFWM) spectra of asymmetric top molecules. New recurrences of J-type with a period of 1/[4(B + C)] are identified in fs DFWM spectra of near-prolate tops SO2 [H. M. Frey, P. Beaud, T. Gerber, B. Mischler, P. P. Radi and A. P. Tzannis, J. Raman Spectrosc., 2000, 31, 71] and NO2 [I. Pastirk, M. Comstock and M. Dantus, Chem. Phys. Lett., 2001, 349, 71]. Our measurements of the asymmetric oblate-like top CH3NO2 revealed new recurrences of A-type with a period of 1/(8A), A, B and C being the rotational constants.The incorporation of nuclear spin statistics into the fs DFWM simulation-fitting code allowed us to successfully reproduce all these new features and the subsequent theoretical analyses uncovered mechanisms of their appearance. The nuclear spin statistics is shown to have a profound effect on fs DFWM spectra of asymmetric top species, notably with several zero spin nuclei.
Riehn
C
C
Johann Wolfgang Goethe-University Frankfurt/M., Institute of Physical and Theoretical Chemistry, Marie-Curie-Str. 11, D-60439 Frankfurt/M, Germany. riehn@chemie.uni-frankfurt.de
Kunitski
M I
MI
Matylitsky
V V
VV
Gelin
M F
MF
Brutschy
B
B