Zeeman transitions

Extensions allowing CPT and Lorentz invariance violations [23] lead to atomic models that reflect the symmetry violations as shifts in the atomic energy levels. It has been argued that such effects can be discovered in the fine-structure of Is — 2s transitions and also in the hyperfine structure of Zeeman transitions. 

Figure 8.17. Low-frequency Zeeman transitions for the c 3nu state of EL, showing the g-factors [35], The top spectrum was obtained from natural H2 (75% ortho, 25% para), and the bottom spectrum was obtained from para-H2. The spectra were obtained by scanning the frequency.

As was pointed out in the introduction, optical detection of the Zeeman transitions of the triplet state preceded the optical detection in zf. Since these former experiments resemble those in ionic crystals, researchers in this field called this technique MODR (microwave-optical double resonance). The assignment of the zf transitions as well as the relative order of the zf levels could be concluded also from the MODR techniques as in the PMDR technique. The first reported MODR experiment was made by Sharnoff (15), in which the Am = 2 transition of the C10D8 tr Plet state in a biphenyl host, using amplitude modulation of the microwave power. A few months later Kwiram reported the optical detection of the Am = + 1 for phenanthrene in biphenyl (16). The experiments were... 

The earlier experiments done on optical detection of the Zeeman transitions were actually focused on determining the zero-field origin of the total intensity of the phosphorescence emission (15-17). The previous workers did not use a spectrometer as a part of their detection system. Fortunately most of the phosphorescence intensity of the systems studied by MODR originates from a single zf level. No optical spectroscopy has been done so far with the MODR methods in spite of the very important information that can be obtained from it. This is probably... 

Under anisotropic conditions, NMR lineshapes for a quadrupolar nucleus are dominated by chemical shielding and (first and second order) quadrupolar interactions. Dipolar interaction is usually a minor contribution only. First-order quadrupole interaction lifts the degeneracy of the allowed 21 (i.e. seven in the case of V / = V2) Zeeman transitions as shown in Figure 3.7, giving rise to seven equidistant lines, viz. a central line (mj = + V2 -V2. unaffected by quadrupole interaction) and six satellite lines. The overall breadth of the spectrum is determined by the size of the nuclear quadrupole coupling constant Cq the deviations from axial symmetry and hence the shape of the spectral envelope are governed by the asymmetry parameter. Static solid-state NMR thus provides additional parameters, in particular the quadrupole coupling constant, which correlates with the electronic situation in a vanadium compound. [ 1 The central component reflects the anisotropy of the chemical shift. 

The strongest Zeeman transition with ETB is the one corresponding to the (0,1,0) state. One notes that the level corresponding to 2pm=+i is associated with the second Landau level, implying that the ionization energy of a QHD in the presence of a magnetic field becomes blurred because the split components can be associated with Landau levels with l > 1. 

It is well known that nmr is a powerful means for the study of the dynamics of polymer chains both in solution and in the solid state. The relaxation of 13C nuclei has been extensively employed for this purpose in this and other laboratories. I illustrate here a dilferent and particularly intriguing approach which as yet has seen only very limited application to synthetic polymers. This is deuterium quadrupolar echo spectroscopy, as employed in our laboratory by Dr. Lynn Jelinski and her collaborators (20). The presence of the nuclear electric quadrupole lifts the degeneracy of the two deuterium Zeeman transitions, and in the solid state produces a very broad (ca 200 kHz) powder pattern of transitions which can be interpreted to yield very specific motional information for those carbons labelled with deuterium. In Figure 7 are shown spectra of poly (butylene terephthalate) deuterated on the central carbons of the aliphatic chains ... 

Doane and Flultsch used a single crystal of NaBrOa to demonstrate the interesting possibility of using the Zeeman-perturbed NQR transitions to modify the signal intensity associated with the Br Zeeman transitions by irradiating the sample at NQR transition frequencies while in a weak magnetic field.This information was subsequently used to determine quadrupolar relaxation transition probabilities. ... 

Figure 8. Power spectrum of Figure 7 after the time domain was digitally filtered.The points are separated by 40 KHz. Four Zeeman transitions are easily resolved.

A final point worth noting is that most steady-state spectrometers use Stark modulation. This modulation gives rise to Stark lobes, which are very helpful for assignments and dipole moment measurements. However, Stark lobes complicate the Zeeman spectrum and can lead to distortion of the Zeeman transitions and the baseline. The Fourier transform spectrometer eliminates this complication. The microwave molecular Zeeman effect in trans-crotonaldehyde has also been reported.16... 

The electric field E(z,t) of the standing light wave causes a shift and broadening of the atomic Zeeman levels (ac Stark shift) that depends on the saturation parameter, which in turn depends on the transition probability, the polarization of E, and the frequency detuning co] — coq. It differs for the different Zeeman transitions. Since the a transition starting from g-1/2 is three times as intense as that from g+1/2 (Fig. 9.28b), the light shift A of g-1/2 is three times the shift A+ of g+1/2. If the... 

A significant drawback of trapping via a LFS Zeeman sublevel is that this opens an exothermic inelastic collision channel. During a collision, a stretched-state [76] LFS molecule can undergo a Zeeman transition to a less-trapped or even HFS state. This process is referred to as either spin relaxation [77] (as in Figure 13.5) or collision-induced Zeeman relaxation. To utilize buffer-gas loading to trap a species, this process must be sufficiently unlikely that the external motion of the molecule can be thermalized and the experiment carried out before the Zeeman state changes. 

There can be an enhancement of the Zeeman transition probability if the interaction time between the trapped species and helium is extended by the formation of a quasibound complex, as is the case for a shape resonance (Figure 13.9). If the temperature of the colliding particles is high enough to permit non-5-wave collisions between particles, there may be quasibound states with nonzero angular momentum... 

The inner product N S depends on the relative projection of N and S, so all states with the same value of Mj = Ms + Mjv also have the same energy under the YsrN S interaction and can be coupled by it. It can be seen that for the rotational ground state, N = 0, Mn = 0 and thus the spin-rotation interaction cannot change Ms without changing Mj. Because Mj is a good quantum number, collisions between helium atoms and molecules in their rotational ground state cannot directly cause spin-depolarization (first-order perturbation theory predicts a Zeeman transition probability of zero). 

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