Rephasing grand

This suggests that a quantum beat spectrum of an AT-level system will, because it contains redundant information, be more complicated than the corresponding frequency domain spectrum. However, when the level spacings are approximately integer multiples of a common factor, such as 2B for upper-state A2F(J) = B (iJ + 2) rotational combination differences, then each upper state (J + 1, J — 1) pair of rotational levels coherently excited from all thermally populated lower-state J" levels contributes to a grand rephasing at tn = n [-gj ] (n = 1,2,...). This is Rotational Coherence Spectroscopy (RCS) (Felker and Zewail, 1987 and 1995 Felker, 1992). It provides upper state rotar tional constants without the need for a rotational analysis. 

Once again, the quadrupole splittings are integer multiples of a common factor, and if several Z/j -components are excited at t — to, the Rydberg wavepacket will precess about N+ and exhibit grand rephasings. 

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