Of NO Rydberg states

Since the formation of high Rydberg states is not a major mechanism in Hj recombination, the presence of electric fields has litde or no effect on the total cross section. This is also the case with the ion-pair reaction since this proceeds via a... 

In alkali atom experiments no explicit resonances have been observed in microwave ionization. However, there are indirect confirmations of the multiphoton resonance picture. First, according to the multiphoton picture the sidebands of the extreme n and n + 1 Stark levels should overlap if E = 1/3n5. In the laser excitation spectrum of Na Rydberg states from the 3p3/2 state in the presence of a 15 GHz microwave field van Linden van den Heuvell et al. observed sidebands spaced by 15.4 GHz, as shown in Fig. 10.15.18 The extent of the sidebands increases linearly with the microwave field, as shown in Fig. 10.15, and the n = 25 and n = 26 sidebands overlap at microwave fields of 150 V/cm or higher, matching the observation that the 25d state has an ionization threshold of 150 V/cm in a 15 GHz field. 

At low n the rate constants for free electron attachment and attachment of Rydberg electrons are no longer the same. In some cases a dependence of the attachment rate constant on the i of the Rydberg state has been observed,89,90 and at low n the rate constant falls below the free electron value.90-92 For... 

No Rydberg state ever exactly corresponds to a pure Hund s case, except at n = 00 or 3, but rather to a situation in an intermediate Hund s case, and it is necessary to choose, to describe it, a basis set corresponding to any one of the pure Hund s cases. The energy terms to be added in each Hund s case are different depending on this choice of basis set. To clarify these choices, consider first the simple case of atoms. 

Uracil has eight n orbitals and two lone pair no orbitals on the two oxygen atoms. The lowest excited states, if we neglect Rydberg states, originate from excitations from these valence orbitals. Figure 11-3 shows the orbitals mainly participating in the first four excited states. The excited states of uracil have been studied theoretically... 

The physical nature of the ZEKE states has been the subject of intense experimental and theoretical investigation in the past several years. In the well-studied case of NO,14,21 we know from the 3 cm-1 red shift of the ZEKE-PFI threshold band relative to the true adiabatic ionization potential (extrapolated from highly accurate measurements of Rydberg series) that the ZEKE states have principal quantum number n 200 and lifetime of 2 (is or longer. Recent work has found ZEKE states with lifetimes as long as 20 ps.22... 

Seen from the point of view of ultra-violet spectroscopy, the situation of aromatic P-, S-, As- and Se-compounds is far more indeterminate than in the t5q)ical oxo and fluoro complexes of the same elements in high oxidation states. Thus, gaseous SFs does not have absorption bands before 95 kK 64) and it is by no means certain that the excited states of these bands involve 3d-orbitals. In many ways, it looks much more as a 4s-like Rydberg state of the whole molecule. 

As an example we can take the excited states of NO. It has been shown that there are two excited states of the same symmetry ( 11) whose vibrational levels are best interpreted on the basis of diabatic curves which cross as in Fig. 1 (75-7 7). One of these states (B) arises from the electron excitation to an antibonding valence molecular orbital and the other (C) from excitation to a Rydberg orbital. The Born-Oppenheimer adiabatic curves cannot cross (by virtue of the non-crossing rule which is to be discussed in a later section) and must fullow the dashed curves shown in the figure. 

Figure I. Lifetime of the n = 3 Rydberg states of NO in Ne, Ar, Kr, and Xe matrices atomic polarizability.

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