2n states

CASSCF calculations for the lowest 2Z+ and 2n state of CCCN in this geometry. 

Fig. 21.16 Observed (X) and calculated ( ) quantum defects of the Ba 6 /2ns states, which are degenerate with the 6p3/212s1/2 state. Note that there is little variation of the quantum defects, unlike what is observed for interacting bound series. The calculated values are from the same model used to produce Fig. 21.15(b) (from ref. 1).

Fig. 23.1 Autoionizing states of doubly excited He below the He+ n = 2 threshold (a) overview, (b) magnification of the n > 6 region, and (c) 2n- states (from ref. 3).

Previous workers had used the molecular beam TOF technique (134) and the VUV flash photolysis LIF technique (135). Ling and Wilson (136) had suggested that either the A(2n) state of CN is produced in the original photolysis process or that I atoms were produced in the Pi/2 and 3/2 states. It had been previously shown (135), by collisional quenching studies, that the A state of CN was not produced. This earlier work has been reviewed by Baronvaski (137) but recently both he and others have done further work on this molecule using excimer laser sources in both static gases and pulsed molecular beams. 

To summarize, the formation of a 2s-energy band from the 2s orbitals when N Li atoms are gathered together to form the Li crystal is shown in Figure 1.15. There are, N 2s-electrons but there are 2N states in the band, therefore the 2s band is only half full. Besides, the atomic Is orbital, which is close to the Li nucleus, that is, is the two Is electrons which are the core electrons, remains undisturbed in the solid, that is, each Li atom has a closed K-shell, specifically a full Is orbital. Consequently, in general, when a solid metal is formed, the external orbitals overlap. As a consequence of this process, the outer electrons move without restraint through the metal, while the core electrons remains in their atomic orbital. 

Hinkley et a/.125 improved these calculations by using Morse and RKR curves to produce vibrational wavefunctions. Using the concept of pure precession they calculated. -1-doubling constants for 2n states of OH, BeH,... 

The bands do not show any diffuseness with a high resolution spectrograph (0.63 A./mm.), indicating that no predissociation takes place in this region.2 However, no /3-emission bands above v = 7 have been observed, probably because of the interaction between the B2II state and the repulsive 22+ state (Fig. 12). Likewise, no emission band of the y system above v = 4 and of the e system above v = 3 have been observed.62 If we accept the view that the emission band is a better criterion for predissociation than the absorption spectrum, predissociation starts above v = 7 of the I 2n state which corresponds to 6.5 e.v. (1910 A.). 

If we are dealing with a 2n state, the possible values of the projection quantum numbers are as follows ... 

Figure 6.18. Transition from case (a) to case (b) for the rotational levels of a regular 2n state.

The evaluation of the matrix elements of these centrifugal distortion corrections appears rather daunting. However, they can be derived quite simply by matrix multiplication. We have already constructed the matrix representations of the two operators involved for a molecule in a 2n state. Since the operator in equation (8.422) consists of... 

As mentioned above, the small mass of OH leads to a pronounced centrifugal distortion of its rotational and spin energy levels. The description of these effects has already been given earlier in section 8.5.4(d), where the exphcit matrix elements for a molecule in a 2n state were given. 

---