Narrow signals

In the case that SWCNTs were produced by laser ablation with Co and Ni, a very weak and narrow signal was superposed on the main broad line. To confirm that this narrow line is associated with SWCNTs, the sample was vacuum-annealed at 1500°C to remove the remaining Co and Ni. 

The [Fe4S4p clusters contain four equivalent irons and give relatively narrow signals (3, 7, 62, 63) (Fig. 2E). The electron relaxation time is evaluated around 5 X 10 s (Table I), which is somewhat smaller than that of the Fe(II) monomer. Also, the signals of [Fe4S4l (15, 64-68) (Fig. 2D) and [Fe4S4fi+ (8, 13, 69-71) (Fig. 2F) systems are sharp. 

In contrast to the narrow signal of H(I), which exhibits a single Lorentzian profile, the feature observed for H(IV) and H(V) was more complex (Fig. 23 lb) with splitting into five lines indicating a superhyperfine structure (line denoted A in Fig. 23 2). This phenomenon is due to the hyperfine interaction between localized spin and two neighboring nitrogen nuclei (nuclear spin... 

The procedures for recording spectra of heteronuclei often differ considerably from those for H and (which would today be considered routine ) since it is necessary, even for routine measurements, to adjust the experimental conditions to suit the special properties of the nuclei to be observed. For example, the spin-lattice relaxation times for some nuclides, such as N, are very long, whereas for others (especially those with an electric quadrupole moment, such as N) they are very short. Also, the spectra observed for some nuclides contain interfering signals caused by other materials present, for example the glass of the sample tube ("B, Si), the spectrometer probe unit ( Al) or the transmitter/receiver coil. For many nuclides the sample temperature and its constancy are important factors for example, quadrupolar nuclides such as O give narrower signals when the temperature is increased. 

The NMR spectra (acetone-iys) of compounds 9-11 show two narrow signals corresponding to N-1 and N-3 of the tetrazine 1,3-dioxide ring, with N-1 appearing as a narrower signal and at lower field (S = —39 ppm, = 20-30 Hz) than N-3 (fi=-45ppm, = 30 5 Hz) <2004RCB2577>. 

MeOAn-ANI-3 NI in the nematic liquid crystal mixture E-7 (Merck) at two orientations of the liquid crystal director, L, taken 700 ns after a 420 nm laser pulse at 150 K. The narrow signal is an expansion of the radical pair signal, (b) Numerical differentiation of the B L L spectrum. 

Figure 1 shows schematically the origin of the narrowed signal. An atom in the 2... 

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