The Neutral Charge State

In the neutral charge state, one expects that the interactions between the two electrons bound to the Ch double donors would give rise to a He-like energy spectrum. However, these double donors are characterized by two electrons with wave functions very different in their spatial extension, and the inner 

4 Prom the Greek chalcos ore , literally ore generating (many sulphides are metallic ores). 

At a difference with the inverted ground state configuration of interstitial Li, the deep ground state of Mg° is Is (Ai). The Mg° spectrum in silicon is shown in Fig. 6.12, together with an unidentified Mg-related complex denoted XMg- This complex has been ascribed to a (Mg,0) centre ([102], and references therein). The spectrum of Mg-diffused silicon also shows electronic lines on the low-energy side of the Mg° spectrum, which have been attributed to another Mg-related centre with an ionization energy of 93meV [152]. No transition toward the even-parity states has been observed for this donor [103]. 

The Ch-related donor spectra differ on that point as several parity-forbidden transitions are observed. They start with symmetry-allowed transitions from the Is ground state to the valley-orbit split Is excited states, and are supplemented with 2s (T2) and 3s (T2) lines and Fano resonances within the photoionization spectrum. This is shown in Fig. 6.13 for Se°. Compared to group-V donors, this extends the energy span of the Ch°-related spectra to the ionization energy of the Is (T2) level (35-40 meV in isolated chalcogens) and it can even increase to 40-48 meV when singlet-triplet spin-forbidden transitions are observed. 

The total spin of the donor electrons of the neutral double donors can be 0 or 1. Repulsion energy is minimized in the ground state for a spin zero state and the singlet to triplet spin transition is in principle forbidden. However, besides the relatively strong ls(Ai) — ls(T2) line, a weak line attributed to the Is (Ai) — Is (3T2) singlet-triplet transition has been observed in Se° and Te° spectra [22,210] Pajot unpublished). The positions and FWHMs of these lines are given in Table 6.12. 

---

For the neutral charge state, the situation is very similar the path through the region of high electron density is favored. However, the low-density path is only 0.2 eV higher now. This seems to indicate that neutral H would be able to move rather freely through the network with very small... 

A AG2980 = -13.7 kcal mol-1, reveals some preference over the successive double ammination of Au+. It is worth noting also that the neutral charge state of Au reverses the order of stability of Au-(NH3)2I and Au-(NH3)2n (Figure 1) the latter appears to be more stable by 4.3 kcal mol-1. This phenomenon will be further discussed in section 4. 

The quantum NOT gate (4) is also realized, within the Hamiltonian //12switch given by Eq. (3), by switching from the neutral charge state of the studied PES to... 

---