Trans attractor

Not shown to the quasi-diabatic potential energy surfaces in Fig. (3) there is a adiabatic potential energy surface. This is distinguished by the maximum at the crossing point nil. The system has a saddle-point structure. In the regions about the cis and trans attractors there is no difference between them. Between 2%1 i... 

The key to get a diabatic electronic state is a strict constraint i.e. keep local symmetry elements invariant. For ethylene, let us start from the cis con-former case. The nuclear geometry of the attractor must be on the (y,z)-plane according to Fig.l. The reaction coordinate must be the dis-rotatory displacement. Due to the nature of the LCAO-MO model in quantum computing chemistry, the closed shell filling of the HOMO must change into a closed shell of the LUMO beyond 0=n/4. The symmetry of the diabatic wave function is hence respected. Mutatis mutandis, the trans conformer wave function before n/4 corresponds to a double filling of the LUMO beyond the n/4 point on fills the HOMO twice. At n/4 there is the diradical singlet and triplet base wavefunctions. 

The nodal planes used qualitatively to discuss cis/trans isomerization clearly appear in the ELF profiles. For AA and BB at the crossing point, the picture reveals the numerical artifact of the adiabatic calculations. At the respective attractors, AA and BB show the expected nodal plane distribution. The method is not capable to distinguish between singlet and triplet spin-state ELF. This issue was discussed during the meeting. The reader may find appropriate discussions in this volume. 

Holmes, P. (1979) A nonlinear oscillator with a strange attractor. Phil. Trans. Roy. Soc. A 292,419. 

A field applied in the —y and —z directions lowers the barrier for the ring opening step, between S-SPl and S-CCCa, from 73.0 kJ/mol (field free) to 61.9 kJ/mol for a field applied in the —y and 60.2 kJ/mol for a field applied in the —z direction (Table 2). A similar trend in the lowering of the barrier is induced by the effect of a nitro group in para to C4—09 bond in spiropyran. The nitro group, being an electron attractor, also depletes the electron density on the C4—09 bond [31]. When the static field is applied in the +y direction, the trans-MC CTCa and TTCa conformers are less stable than SP by 42.5 and 20.8 kJ/mol, respectively, while when the field applied in the —z direction, the CTCa and TTCa conformers are less stable than S-SPl by 27.2 and 16.4 kJ/mol but more stable than in the field-free case (see Table 2). On the other hand, a field... 

---