Rydberg states optical excitation

In addition to the steplike features of the spectra in fig. 4 and 5 the distinct resonace peaks have to be discussed. As already mentioned these peaks are expected to be autoionizing contributions of vibronic Rydberg states, (vibrationally) excited above the ionization potential of 9.241 eV, which can be optically excited from the electronic ground-state and therefore must have symmetries a or e. Additionally there is a close lying e (n = 3)-Rydberg lev at 9. i6 eV (-653 cm ) belonging to an excitation of an e -a-electron with a series limit of 11.49 eV. 

The inherent resolution of collinear-beam spectroscopy is still limited by the residual Doppler broadening. In beams with a broad velocity distribution the labeling of one velocity class by optical pumping, probed in a second Doppler-tuning zone, was exploited already before narrow Doppler widths were achieved. The complete elimination of the first-order Doppler effect in resonant two-photon absorption on Ne I has been discussed in Section 3.3, in connection with a precision measurement of the relativistic Doppler effect. A similar experiment was performed on In I, where the 29p Rydberg state was excited from 5p Pi/2 via 6s Si/2 and detected by field ionization. The linewidth caused by the laser jitter can be reduced to the transit-time limit of a few hundred kilohertz. 

E. W. Schlag The pickup is from a sea of ions of one species that picks up the ZEKE electron of the other species. Thus it shows up at the wrong energy. When the sea of ions is shut off, the signal disappears since it is at the wrong mass. This demonstrates that ZEKE states have an existence of their own and need not be formed necessarily from optically excited low-/ Rydberg states. 

There can be a difference between the dissociation of polyatomic molecules and delayed ionization in the nature of the initial excitation. In ZEKE spectroscopy the state that is optically accessed (typically via an intermediate resonantly excited state) is a high Rydberg state, that is a state where most of the available energy is electronic excitation. Such a state is typically directly coupled to the continuum and can promptly ionize, unlike the typical preparation process in a unimolecular dissociation where the state initially accessed does not have much of its energy already along the reaction coordinate. It is quite possible however to observe delayed ionization in molecules that have acquired their energy by other means so that the difference, while certainly important is not one of principle. 

A particular illustration of this cross-cultural influence is the question of whether one can pump states directly coupled to the transition state. In the Rydberg problem the answer is very much yes because these are often the states that are optically excited. They are directly coupled to the continuum but are also coupled to other Rydberg series, where n is lower and the core is more excited. 

Purely optical excitation is possible for alkali and alkaline earth atoms. For most other atoms the transition from the ground state to any other level is at too short a wavelength to be useful. To produce Rydberg states of such atoms a combination of collisional and optical excitation is quite effective. A good example is the study of the Rydberg states of Xe by Stebbings et al.24 As shown in Fig. 3.5, a thermal beam of Xe atoms is excited by electron impact, and a reasonable fraction of the excited atoms is left in the metastable state. Downstream from the electron excitation the atoms in the metastable state are excited to a Rydberg state by pulsed dye laser excitation. 

Usually the H Rydberg states are not prepared in the zero field parabolic states, but in the spherical states by, for example, optical excitation. In this case, when the field is applied we would expect it to project the single n(m state onto the degenerate nn m states, each of which would then follow its own path to... 

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