Quadrupole coupling interaction schemes

We deal first with the 14N quadrupole interaction, using the first term in (10.88), and making use of the results described in chapter 8 for the weak field coupled basis in CsF. The nuclear spin coupling scheme is... 

Figure 2 Spectrum of the 7 = 8-7 rotational transition of Xe Cu Cl. The compUcated hyperfine structure arises from nuclear quadrupole interactions of Cu (7cu = 3/2) and C1 (7qi = 3/2). All transitions are spUt into Doppler doublets as a result of the molecular expansion traveling parallel to the microwave cavity axis. For clarity of the picture, the quantum number assignments of only a few hyperfine components are given as Fj -F/, F -F". The angular momentum coupling scheme Fi = Icu + J F = Fi + Iq was used. The compound was produced using laser ablation of a copper rod in a molecular expansion of a mixture of 0.1% CI2, 15% Xe, and 85% Ar. The particular isotopomer was measured in its natural abundance of 6.3%. This spectmm was recorded using 15 000 averaging cycles with a total accumulation time of about 3.5 h...

The hyperfine splitting arises from the nuclear electric quadrupole interaction. The coupling scheme is F = J + /c. ... 

The physical origins of the effect can be illustrated from Figure 2, which shows the energy level scheme for an I = 1 nucleus, such as coupled to an S = 1/2 electron spin. In the case considered here (i.e., the electron-nuclear interaction, the nuclear Zeeman interaction, and the nuclear quadrupole interaction, all of the same order), microwaves can induce both allowed and semi-forbidden transitions between states in the Mj = 1/2 manifold (a) and the Ms = - 1/2 manifold (/ ). Simultaneous excitation of both kinds of transitions by the echo generating microwave pulses gives rise to interference effects, which manifest themselves as variations in the echo amplitude and thus cause the modulation of the echo envelope. Where a number of nuclei are coupled to the same electron spin, the level scheme becomes more complicated, but it is possible to factor out contributions due to coupling with each nucleus in the overall modulation pattern. If v(U l2>" n) is the modulation function due due to coupling with n nuclei, then... 

Marsella and coworkers exploited perfluorophenyl-phenyl quadrupole interactions to template the synthesis of a thiophene-containing cyclophane [44]. As shown in Scheme 6.14, when the oligomeric precursors 98-101 were treated with Sonogashira cross-coupling conditions, the mixed perfluorophenyl-phenyl cyclophane 102 was reproducibly achieved in greater yield than either of the symmetrical analogs 103 and 104. Other mixed macrocyclic derivatives were also prepared as part of this study, and their findings with these model systems supported... 

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