1A states

Fig.l. Poiential energy curves including the Davidson correction of the X ll, A Ifl and 1a states of PN... 

The 1A state crosses over to another state, probably the ground state, X /4, by internal conversion within 0.4 nsec... 

Whilst the most important examples of Zeeman and Stark effects in 1A states are found in molecular beam studies, they can also be important in conventional absorption microwave rotational spectroscopy, as we describe in chapter 10. The use of the Stark effect to determine molecular dipole moments is a very important example. 

In summary, we can write down the effective Hamiltonian which represents the fine-structure terms for a diatomic molecule in a 25+1A state as ... 

In the second line of (9.4) we have transformed from space to molecule-fixed axes (q). If we now retain only terms diagonal in the 1A state by putting q = 0, we obtain the diagonal and off-diagonal Zeeman matrix elements, as follows ... 

Terms describing the Zeeman and magnetic hyperfine interactions must be added to (9.172). The complete Zeeman Hamiltonian for a molecule in a 25+1A state is given by Nelis, Beaton, Evenson and Brown [76] as... 

We discussed the Zeeman effect for 1A states in chapter 9, particularly with reference to SO where it provides a particularly simple example with which to illustrate the... 

In the case of the Cr(CO)5 or Fe(CO)4 fragments a Jahn-Teller induced surface intersection between the Sj and S0 states explains the rapid transition to the S state following excitation of the parent. However for the Ni(CO)3 fragment the ground state is the 1A state and this has a planar structure (D3A). The first excited state Sj is the degenerate lE" state which splits by planar distortion producing 1Bl and A, states but not an Al state at the C2v limit. Consequently such a distortion does not provide a deactivation route to the S0 surface of Ni(CO)3. The Ni(CO)3 fragment remains in its Sl state which explains the luminescence observed in this system. 

A State whether the following processes represent open or closed systems. 

Perhaps the most abundant metastable state in the upper atmosphere is the (a 1A ) state of oxygen, which is produced in the D region by the... 

Both Ok and fl. - flj. provide useful insights into the causes and rates of specific dynamical processes. Sections 9.4.9 and 9.4.10 provide analyses of the dynamics of the S-uncoupling operator in a 25+1A state and the 1 2 anharmonic coupling operator that contributes to Intramolecular Vibrational Redistribution (IVR) in a polyatomic molecule and illustrate the diagnostic power of the flk + fij. and lk — resonance and rate operators. 

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