Ei S3 4 67 H x08

Fig. 12J. Electronic levels (in units of eV) for (a) the neutral C70 molecule [12.22,40], (b) the molecular ion C70 [12.19], and (c) the molecular ion [12.22,41]. The various cal-culational schemes have largely focused on the bond lengths and the position of the LUMO levels (particularly for the neutral molecule). Calculations for the LUMO levels must be regarded as more uncertain than for the HOMO levels. The levels for the neutral molecule have been shifted to coincide with the anions.

symmetry suggests an lA\ ground state with excited triplet states 3A'2 and 3E2 and excited singlet states lA\, XE[, and lE'2, referring to the discussion of §4.4.1.

From the above discussion, we expect the ground state of C7Q to have an ... a2e*a'2 configuration with XA\ symmetry (see Table 12.6). Also listed in this table are the level designations for the ground state multiplets for the various ions C"^ (—6 < n < +6), first neglecting spin-orbit coupling (column 3) and then including spin-orbit coupling (column 4) under the heading Fine Structure. Excitonic excited states are thus expected to have an a'2a'\ configuration, which would have a XA'2 and a 3A'2 excitonic excited state symmetry. The electronic structure of the Cy0 ion has been calculated

Table 12.6

Multiplet structures of the ground states of C70 (low spin state) [12.22],

Table 12.6

Multiplet structures of the ground states of C70 (low spin state) [12.22],

n

Configuration

D5h state"

Fine Structure

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