Ionization experiment static

The experiment is done using the apparatus shown in Fig. 10.2. Two tunable dye lasers are used to excite K atoms in a beam to the (n + 2)s state. A static field can be applied to vary the separation between the 18s and (16,k) states. The atoms are exposed to a microwave pulse, and subsequently to a field ionization pulse which ionizes atoms in the (n,k) Stark state, but not those in the (n + 2)s state. The (n,k) field ionization signal is then monitored as either the microwave field amplitude or the static field is swept over many shots of the laser. To the extent that both Stark shifts are linear, the static field alters the energy separation between the two states, but not their wavefunctions. 

The ionization curve of Fig. 10.18 is obtained in the same way as the data shown in Fig. 10.14, by exciting atoms in zero field and then exposing them to a strong microwave field. When atoms are excited in the presence of a static field, to a single Stark state, and held in single Stark state by the continued application of the field, resonances became more apparent when a microwave field in the same direction is applied. Bayfield and Pinnaduwage have observed transitions from the extreme red H n = 60, m = 0 Stark state to other nearby extreme Stark states in static fields of 5-10 V/cm.29 As shown by Fig. 10.19 resonances corresponding to the four photon transition to the extreme red n = 61 Stark state and four and five photon transitions to the extreme red n = 59 Stark state are visible. These experiments are similar to the K and He multiphoton resonance experiments described earlier, but are inherently simpler because the extreme red n = 60 Stark state is only coupled to the extreme n = 59 Stark state. In contrast, the K (n + 2)s state is coupled to all the (n,k) Stark states. 

Details of the collision-induced dissociation (CID) experiments have been described [26]. Argon was used as the collision gas at a total pressure of "4 x 10-t> torr. The collision energy of the ions can be varied (typically between 0 and 100 eV). A Bayard-Alpert ionization gauge was used to monitor static pressures. 

The earliest experiments on the resonance stepwise photoionization of molecules (H2CO) were conducted by Andreyev et al. (1975) in an ionization chamber without using any mass separation of the photoions produced. The next natural step was the two-stage resonance photoionization of molecules by the scheme of Fig. 10.1, involving mass analysis of the photoions produced (Antonov et al. 1977, 1978). The experimental setup for studying the stepwise photoionization of polyatomic molecules in a mass spectrometer consisted of a static magnetic mass spectrometer and time-synchronized... 

The details of the X-ray structure of the RC allow substantial modelling of the acceptor quinone functions, albeit limited by the static nature of the structural data, and some efforts have been put into calculation of the pK properties and protonation states of the ionizable residues of the protein [15,16]. The results are not inconsistent with experiment but consideration of all pairwise interactions, as required in these calculations, renders them largely inaccessible to any intuitive considerations. Here, we explore the use of a simple model to describe the behavior of the acceptor quinones in terms of pairwise electrostatic interactions of a small number of components, amenable to some intuitive conceptualization. 

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