Radial-field sidebands in MAS

The existence of sidebands at +/-v(r) in MAS spectra due to the radial component of the RF field at the edges of the coil is described theoretically and illustrated experimentally. The height of the radial-field sidebands does not depend on the spinning speed and may contribute significantly to the intensity of -1 spinning sideband of MAS modulated internal interactions for a sample placed in a rotor of length exceeding the solenoid coil or a small volume sample placed at the edge of the coil.     

Adiabatic decoupling sidebands

An analytical solution is given for amplitudes and phases of adiabatic decoupling sidebands as a function of spin inversion time tau. Since all the adiabatic decoupling phases theta(t, tau) refocus at two periods (2T) of the decoupling pulse, the sidebands are located at n/2T rather than at n/T as observed in other decoupling schemes. The real (R(n)(tau)) and imaginary (I(n)(tau)) amplitudes of the sidebands have symmetry R(n)(tau) = R(-n)(tau) and I(n)(tau) = -I(-n)(tau), forming a mirror image between the counterparts of the sidebands. When frequency sweep changes direction all I(n)(tau) are inverted while all R(n)(tau) remain unchanged, leading to pure absorption sidebands with two accumulations as demonstrated by Kupce and Freeman, and to an exchange of sidebands between counterparts. The sum of the real parts for sidebands n = 1 and 2 is almost a constant near on-resonance decoupling, and it increases substantially for large decoupling offsets. The phase defocusing can be minimized for all decoupling offsets by inserting an initial decoupling period with T(ini) = T/2, eliminating all sidebands located at n/2T (n = +/-1, +/-3, +/-5, ...).     

Modulation-induced sidebands in magnetic resonance

The induced transition probability between Zeeman levels was calculated in the case of a nuclear spin under a modulated magnetic field. It was shown that the intensities of the sidebands can be accurately calculated for a given lineshape of the signal when no significant saturation occurs. This result suggested a technique for accurately measuring the modulation amplitude of magnetic fields. This suggestion was confirmed experimentally in the case of an rf field produced by an ENDOR coil. A quantum-mechanical explanation for the production of sidebands was also found during the course of this calculation.     

Multi-magnon luminescence sidebands in antiferromagnets

Using pulsed excitation and detection, we have observed multi-magnon (? 7) luminescence sidebands of the ⁴T_1g (⁴G) → ⁶A_1g (⁶S) excitonic transition in MnF₂, KMnF₃, and RbMnF₃. A simple model is proposed to explain the results qualitatively.     

Spectroscopy with modulation sidebands

An optical-optical double resonance method for obtaining resolution inside the Doppler width is developed. In this method one of optical frequencies is generated as a modulation sideband. Using a Pockels cell modulator, the experiment has been demonstrated on the ground state Zeeman levels of the Na atom.     

Spin-echo modulation in ruby

Electron-spin echoes in ruby at X and Ku band are observed with high definition and high signal-to-noise ratio. Comparison of experimental and theoretical echo envelopes provides confirmation of recent ENDOR work.     

Temperature dependence of hot magnon sidebands in antiferromagnets

The temperature dependence of the absorption intensity of hot magnon sidebands is investigated for the two-dimensional (2D) antiferromagnet BaMnF₄, and the 3D antiferromagnet MnF₂. A general expression for the temperature dependence is presented for 1D, 2D and 3D antiferromagnets.     

Relative CSA-dipolar orientation from REDOR sidebands

Algebraic expressions are given for the sideband intensities of REDOR dephasing experiments as a function of the relative orientation of the CSA and dipolar tensors. The expressions are straightforward to derive and implement and can be easily modified for variations in the spin systems, including distributions of distances and multiple dephasers. These expressions, along with the high sensitivity, resolution, and general robust nature of REDOR, make determining CSA-dipolar orientations from REDOR experiments reliable and, compared to full simulations, efficient and routine. Additionally, it is shown that even the +/-1 sidebands of fast-spinning samples may contain significant information about orientation. Finally, numerical integration of the expressions supports the intuitive notion that any difference in the sideband dephasing rates is evidence of preferred CSA-dipolar orientations. This fact can be used to gauge the extent of local molecular order in intermolecular dephasing experiments.     

Removal of sidebands in double-rotation NMR in real time

Double-rotation (DOR) is the only technique generally capable of yielding high-resolution NMR spectra of half-integer quadrupolar nuclei in one dimension for solids without the need for sophisticated coherence pathway selection. Unfortunately, due to the low outer rotor spinning frequencies currently available, the spectra often contain a large number of spinning sidebands which may overlap with the resonances of interest. We implement a simple, robust, and easy to use family of pulse sequences, which in practice are fully analogous to the 'total suppression of sidebands' (TOSS) sequences, to suppress all sidebands arising from the spinning of the outer rotor in DOR experiments. By removing the rotor phase dependence of the evolution of the sidebands, the sidebands destructively interfere with one another during the course of signal averaging to yield 'solution-like' spectra of half-integer quadrupolar nuclei in solids. Advantages and shortcomings of the method compared to other DOR sideband suppression methods are explored with the aid of simulations.     

Optical inhomogeneities in ruby crystals

The optical inhomogeneities in ruby laser crystals, resulting from inhomogeneity of the chromium concentration, from various glide paths, and from the presence of disoriented blocks, are investigated. It is shown that the most harmful influence on the characteristics of laser damage is exerted by the axially asymmetrical part of the refractive index distortion due to residual mechanical stresses. A correlation is obtained between the inhomogeneity of the refractive index and the laser beam divergence. A method is proposed for improving the optical inhomogeneity of the ruby laser crystals by high-temperature (diffusion) annealing.Translated from Trudy Ordena Lenina Fizicheskogo Instituta im. P. N. Lebedeva, Vol. 101, pp. 130–147, 1978.     

Orientational information from TEDOR spectral sidebands.

In a dipolar-coupled spin-1/2 network of the type 15N1-(13)C-15N2, an assessment of the sensitivity of the N --> C and C --> N TEDOR sideband intensities to the Euler angles defining the orientation of the two heteronuclear dipolar vectors in the 13C and 15N chemical shift (CS) tensor principal axes system has been carried out via numerical calculations. The results clearly indicate the potential of TEDOR MAS NMR spectroscopy for the characterization of the CS tensor orientation in the molecular frame. The efficacy of the method has been experimentally illustrated by TEDOR studies on a polycrystalline sample of [1, 3-(15)N2, 2-(13)C]uracil, which is one of the four bases in RNA.     

Rotational sidebands in 166Er

Rotational sidebands in ¹⁶⁶Er were observed using the 24 MeV ¹⁶⁴Dy(α, 2nγ) reactions. The ground-state band was observed up to spin 16⁺ and does not backbend. A strong backbend is, however, observed in a K^π = (O⁺) sideband, indicating that the 12⁺ state of the previously unknown S-band is at 2656 keV. The γ-band shows significant rotational alignment above I = 10⁺. Levels of at least two negative-parity bands, one of which is primarily the K^π = 2^? octupole vibration, are also observed.     

Vibrational sidebands and the Kondo effect in molecular transistors

Electron transport through molecular quantum dots coupled to a single vibrational mode is studied in the Kondo regime. We apply a generalized Schrieffer-Wolff transformation to determine the effective low-energy spin-spin-vibron interaction. From this model we calculate the nonlinear conductance and find Kondo sidebands located at bias voltages equal to multiples of the vibron frequency. Because of selection rules, the side peaks are found to have strong gate-voltage dependences, which can be tested experimentally. In the limit of weak electron-vibron coupling, we employ a perturbative renormalization group scheme to calculate analytically the nonlinear conductance.