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A 2D plot of a spectrum with relatively large (±25 MHz) spectral width containing many narrow lines of widths (FWHM) below 200 kHz can be improved noticeably by invoking Linear Prediction (LP) for FID reconstruction and zero-filling with respect to spectral resolution and weak peak detection capability. This was demonstrated by a comparison of two 2D contour plots calculated with and without the help of linear prediction singular value decomposition and zero-filling.

A UV (300-400 nm) photoactivated TiO{sub 2} suspension in a (1:1) mixture of toluene and methanol at 295 K was found to be a very effective system for generating fullerene radicals in high concentrations with good reproducibility. The primary generated radical A is characterized by a single-line EPR spectrum (g = 2.0000 and peak-to-peak width (pp) = 0.09 mT). After an induction period, the formation of an additional paramagnetic product B with g = 2.0006 and pp = 0.042 mT is observed. Higher ratios of fullerene:TiO{sub 2} and shorter irradiation periods favor the formation of radical A. Both radicals A and B were also generated via in-situ cathodic reduction and in both systems (TiO{sub 2} and electrolytic) were found to be similar with respect to g factor, line width, and saturation behavior. Using fullerene enriched to 7% in {sup 13}C, the line width of A increased from 0.09 to 0.17 mT. Lowering the temperature, line A was narrowed from pp(300 K) = 0.095 to pp(180 K) = 0.032 mT and at 150 K became asymmetric. At 100 K the observed spectrum is well described by an axially symmetric g matrix with g** - g* = 0.0008. Analogous VIS/NIR measurements withmore » an intensive line at 1075 mnm confirm that in the EPR investigations radical A is a monoanion of C{sub 60}. 38 refs., 12 figs.« less

Co-doping of Li/MgO, a well-known catalyst for the oxidative coupling of methane, was investigated. It is demonstrated that Gd3+ and Fe3+ can be used as spin sensors in these solids to investigate the structure via EPR spectroscopy. These aliovalent ions occupy Mg2+ sites in the lattice; the expected coupling with charge-compensating neighboring Li+ was detected. A strong increase of the activity was observed. However, all samples suffered from deactivation. The solubility of Gd3+ in MgO turned out to be inhibited. No such restriction was observed for Fe3+.

Utilizing highly polar solvents for the stabilization of Fullerene anions, electrochemical and chemical reduction resulted in narrow single line EPR spectra for the monoanions of C60 and C70 being characterized byg=2.0001(1), ΔB=0.075 mT,g=2.0019(1), ΔB=0.016 mT, respectively. Apparently, the orbital degeneracy of the C60 monoanion is lifted under these conditions to such an extent, that the abnormal large spin lattice relaxation rate believed to be responsible for the approximately 5 mT line width of the monoanion is sufficiently reduced.13C enrichment resulted in noticeable line broadening, allowing an estimate of the average13C hyperfine coupling constantaave=0.1 mT.

A study of the photoexcited triplet state of C[sub 60] ([sup 3]C[sub 60]) in liquid solution (toluene, methylcyclohexane) was made using pulsed-EPR techniques. The spin-lattice relaxation time (T[sub 1]), phase-memory time (T[sub m]), and line width ([Delta][nu][sub 1/2]) were measured as function of temperature (170-360 K). The results were used to analyze some aspects of the spin dynamics of [sup 3]C[sub 60]. The data confirm earlier findings that the relaxation toward Boltzmann equilibrium is responsible for the initial growth of the signal amplitude when FT-EPR spectra are measured as a function of delay time between laser excitation and [pi]/2 microwave pulse. Also, it is found that [Delta][nu][sub 1/2] = 1/[pi]T[sub m] in both solvents over the whole temperature range. This establishes that there is a negligible contribution to the line width from unresolved [sup 13]C hyperfine structure. The contribution of the electron spin-spin interaction modulated by rotational motion to the relaxation rates is analyzed. The analysis shows that the value of the zero-field splitting parameter D, which determines the magnitude of this contribution, is about an order of magnitude less than that found in rigid matrices at low temperature. 26 refs., 9 figs., 1 tab.

We herein report the investigation of N@C(60) exposed to laser flash excitation to exhibit the acceleration of the decay of (N@C(60))* by the encased N atom.

We report on the observation of two different triplet states in photoexcited C 60 fullerene molecules. The following fine structure parameters were determined from spectral fits to the triplet powder spectrum: | D 1 | = 0.0117 cm −1 (12.5 mT), | E 1 | = 0.0014 cm −1 (1.5 mT) and | D 2 | = 0.0047 cm −1 (5 mT), | E 2 | = 0.0 cm −1 . Below 10 K mainly triplet 1 was observed, whereas triplet 2 appeared only with increasing temperature. It is thermally activated with an activation energy Δ E ≈ 17 meV. Due to motional narrowing the parameters D 1 and E 1 decrease slightly at higher temperatures. Depopulation kinetics as well as spin-lattice relaxation rates were determined.

Utilizing the high time and phase resolution of Fourier transform electron paramagnetic resonance, the buildup and decay kinetics of the transient radical pair Zn tetraphenylporphyrin+/Duroquinone− in ethanol could be studied by detecting the dispersive component in the Fourier transformed free induction decays of the fully separated radical anions. The dispersive line components originate from the exchange coupling J of the radical pair in its metastable state trapped by an attractive temperature dependent Coulomb interaction U(rc,T) at an equilibrium distance rc. The decay rate constant kd into free ions was studied over the temperature range of 225–298 K and varied from kd=3.2×106 to 10×106 s−1. This change in kd could be fully rationalized in terms of the temperature dependence of the solvent dielectric constant (leading to a variation of the cage potential from 0.07 to 0.12 eV) and the diffusion constant. The buildup rate constants were consistent with the assumption of a diffusion‐controlled electro...

Highly resolved EPR transitions displaying deuteron hyperfine effects in di- p -bromobenzophenone in a single crystal host have been recorded with the technique of electron spin echo envelope modulation (ESEEM). Orientation dependence of the observed line positions under variation of the external magnetic field in the crystallographic a, c -plane yielded the magnetic dipolar and deuteron quadrupole coupling matrices for deuterons at two positions in the molecule. The strong orientational dependence of the line intensities in the Fourier-transformed ESEEM decay could be fully accounted for by calculating the echo modulation amplitudes numerically, using these matrices.

The electromagnetic properties of a bulk sample of high quality single-wall carbon nanotubes with a mean diameter of 2.5 nm were investigated by noninvasive methods. The observed sudden increase in the microwave absorptivity below 12 K is taken as indicative of the formation of a superconducting phase of a small part of the sample. The increase in the ac susceptibility peaking at 20 K points to the existence of a weak ferromagnetism probably of a different set of tubes in the heterogeneous sample. Above 20 K, the microwave loss function apparently originates predominantly from a narrow-band-gap 7 meV one-dimensional conductor.

Multifrequency electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) techniques were used to obtain structural information about the copper(II)-chelidamate complex. Well-resolved nitrogen ENDOR spectra could be recorded from solid solution samples by using selective excitation of spin packets. Evaluation of nuclear quadrupole and dipolar hyperfine interaction of the directly ligated nitrogen allowed for an identification of the bond direction to the copper ion within the eigen frame of the copper g-matrix. Invoking two-dimensional EPR techniques, additional hyperfine interaction with a "distant" nitrogen spin, identified as resulting from the solvent dimethylformamide (DMF), was observed. The experimental data are only consistent with formation of a stable pseudoplanar copper complex with single solvent ligation via its oxygen atom.

Immediately after the observation that fullerenes can act as cages for persistent trapping of ions or atoms, Electron Paramagnetic Resonance (EPR) was used for the investigation of these compounds. In contrast to group 15 atoms entrapped in C 60 or C 70 , which are nearly perfectly decoupled from the cage and which at time average are found at the center of the cage, it was observed that single lanthanide ions are localized at specific binding sites of the internal carbon surface. Apparently this is no longer true for encased ion clusters like La 6+ 2 or Sc 3 N 6+ , which are exploring the full inner space of the fullerenes in such a way that the inherent symmetry of the cage is retained. Although simple 2-pulse sequences have been used to elucidate ion and cage motions in the single ion case, more advanced techniques like pulsed electron-nuclear double resonance (ENDOR) as well as two-dimensional EPR had to be invoked for the study of the cluster compounds. Performing experiments at 95 GHz, one is benefiting from superior spectrometer sensitivity as well as from the inherent capability for improved orientation selection. In this contribution results about Sc 3 N@C - 80 , La@C 82 , and La 2 @C - 80 compounds are compiled. It was the purpose of our investigation to obtain information about the amount of spin and charge transfer in these cage compounds. Using DFT methods, a reasonable description of the observed spin Hamilton parameters could be obtained.

The double-bridged hemicarcerand [A,B-(CH2OH)2-cavitand]-(CH2NHCH2)2-[A,B-(CH2OH)2-cavitand] 23 (and several other related compounds) was synthesized by the condensation of the two complementary precursors A,B-(CH2NH2)2(CH2OH)2-cavitand and A,B-(CH2Br)2(CH2OAc)2-cavitand followed by hydrolysis of the acetate groups. This hemicarcerand has nitrogen and oxygen donor atoms located on the interior of the spherical cavity and thus allows endohedral coordination of metal ions. The cavity has a volume of approximately 0.12 nm3, a value obtained by calculating a Connolly-type contact surface and the molecular electrostatic potential. The Cu2+ complex of hemicarcerand 23 was studied in detail by EPR and DFT calculations at the UB3LYP/6-31G level to verify the anticipated endohedral nature of the metal complex. It could be shown that the copper ion is coordinated to four oxygen donor atoms and no deviation from axial symmetry at the copper site could be detected. No direct coordination to nitrogen atoms of the hemicarcerand could be observed; however, complexation with DMF solvent molecules was detected by ESEEM and HYSCORE experiments. The closed structure of the hemicarcerand was also confirmed by an evaluation of proton-copper distances. Results from DFT calculations are in accord with the EPR results, and further support suggested coordination of the Cu(II) within the hemicarcerand cavity by four oxygen donor atoms.

By utilizing multifrequency electron paramagnetic resonance (EPR) spectroscopy, the iron functional center in ${\mathrm{Fe}}^{3+}$-modified polycrystalline lead zirconate $(\mathrm{Pb}\mathrm{Zr}{\mathrm{O}}_{3})$ was studied. The single phase polycrystalline sample remained orthorhombic and antiferroelectric down to $20\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ as confirmed by high-resolution synchrotron powder diffraction. The ${\mathrm{Fe}}^{3+}$ ions were identified as substituting for ${\mathrm{Zr}}^{4+}$ at the B-site of the perovskite $\mathrm{AB}{\mathrm{O}}_{3}$ lattice. Similarly as found for ${\mathrm{Fe}}^{3+}:\mathrm{Pb}\mathrm{Ti}{\mathrm{O}}_{3}$ [Me\ifmmode \check{s}\else \v{s}\fi{}tri\ifmmode \acute{c}\else \'{c}\fi{} et al., Phys. Rev. B 71, 134109 (2005)], the value of the fine-structure (FS) parameter ${B}_{2}^{0}$ is only consistent with a model in which a charged ${({\mathrm{Fe}}_{\mathrm{Zr}}^{\ensuremath{'}}\char21{}{V}_{\mathrm{O}}^{\ifmmode\bullet\else\textbullet\fi{}\ifmmode\bullet\else\textbullet\fi{}})}^{\ifmmode\bullet\else\textbullet\fi{}}$ defect associate is formed. In contrast to a well defined iron functional center in lead titanate $(\mathrm{Pb}\mathrm{Ti}{\mathrm{O}}_{3})$ with FS parameters exhibiting variances of less than 3%, a strong broadening of the EPR powder pattern was observed in lead zirconate, indicating a much larger variance of FS parameters. It is suggested that the apparent broad distribution of fine-structure parameters arises from the system's capability to realize different oxygen vacancy positions in the first coordination shell around the iron site. This proposed model of a small number of distinct iron-oxygen vacancy sites is supported by the observation that corresponding ${B}_{2}^{0}$ and orthorhombic ${B}_{2}^{2}$ FS parameters of these sites are anticorrelated, a property not expected for random distributions of fine-structure parameters.

The ${\mathrm{Fe}}^{3+}$ center in ferroelectric $\mathrm{Pb}\mathrm{Ti}{\mathrm{O}}_{3}$ together with an oxygen vacancy forms a charged defect associate, oriented along the crystallographic $c$ axis. Its microscopic structure has been analyzed in detail comparing results from a semiempirical Newman superposition model analysis based on fine-structure data and from calculations using density functional theory. Both methods give evidence for a substitution of ${\mathrm{Fe}}^{3+}$ for ${\mathrm{Ti}}^{4+}$ as an acceptor center. The position of the iron ion in the ferroelectric phase is found to be similar to the $B$ site in the paraelectric phase. Partial charge compensation is locally provided by a directly coordinated oxygen vacancy. Using high-resolution synchrotron powder diffraction, it was verified that lead titanate remains tetragonal down to $12\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, exhibiting a $c∕a$ ratio of 1.0721.

Copper(II)- and iron(III)-modified Pb[Zr(x)Ti(1-x)]O3 ferroelectrics were investigated by means of high-field/high-frequency EPR. The results obtained suggest that Cu2+ and Fe3+ both substitute as acceptor centers for [Zr,Ti]4+. Whereas for the iron-doped system the charge compensating oxygen vacancies (V(O)**) lead to the formation of charged (Fe'(Ti-)V(O)**)* defect associates, no such associates have been observed for the copper-modified system. As regards the morphotropic phase boundary, the model of a mesoscopic mixing of the pure-member phases has been refined to a picture in which a nanoscale composition distribution prevails.

Using the quartet spin of encased nitrogen atoms as an electron paramagnetic resonance (EPR) probe, it is possible to examine the fullerene/nanotube interactions in a peapod. A purification method is developed which allows low temperature filling of nanotubes with endohedral fullerenes. The paramagnetic impurities of undoped single wall carbon nanotubes (SWNT) are characterized via EPR resulting in a broad superparamagnetic signal of the remaining catalyst particles and a rather narrow signal of carbonaceous material. Comparison of EPR spectra of several nitrogen endohedral doped peapods with their analogues obtained in a solid fullerene matrix shows a significant broadening of N@C60 and N@C70 EPR signals. This broadening is related to a non‐vanishing zero‐field splitting caused by deformation of the fullerene cage upon encapsulation.

Heterodisulfide reductase (Hdr) from methanogenic archea is an iron-sulfur protein that catalyzes the reversible two-electron reduction of the mixed disulfide CoM-S-S-CoB to the thiol coenzymes, coenzyme M (CoM-SH) and coenzyme B (CoB-SH). It is unusual that this enzyme uses an iron-sulfur cluster to mediate disulfide reduction in two one-electron steps via site-specific cluster chemistry. Upon half-reaction of the oxidized enzyme with CoM-SH in the absence of CoB-SH, an iron-based paramagnetic intermediate is formed, designated CoM-Hdr. In this Communication we report 57Fe pulsed ENDOR at two very different frequencies, 9 and 94 GHz, that identify the iron sites of CoM-Hdr. We find direct evidence for a [4Fe-4S]3+ cluster, and we determine the sign of the 57Fe hyperfine couplings. The 57Fe isotropic hfc values suggest a complex interaction between the cluster and the CoM-SH substrate.

Using pulsed EPR techniques, the basic spin relaxation properties of N@C60‐based peapods were determined. In contrast to narrow line spectra typical for N@C60 in solid solution or in a C60 matrix, substantial line broadening is observed for the SWCNT‐encapsulated N@C60 molecules, which might be indicative for uniaxial cage distortion by interaction with the nanotube.

It is demonstrated that metallo‐endofullerenes can exhibit close‐lying electronic levels with different spin multiplicity, thus serving as sensitive spin probes for charge transfer in carbon nanotubes. In contrast, N@C60 is an inert spin label with exceptional sensitivity against local electric fields, which can probably be used to explore SWNT properties.

Endohedral fullerenes N@C 60 and N@C 70 were dissolved in the liquid crystal 4-methoxybenzylidene-4′- n -butylaniline (MBBA) and investigated by electron paramagnetic resonance. In both cases well resolved EPR spectra give proof for molecular orientation in the nematic mesophase. Spectral features are dominated by a nonvanishing zero-field interaction, indicating a deviation from spherical spin density distribution at the encased nitrogen atom. In N@C 70 , a maximum order parameter O 33 =0.18(3), correlated with the long axis of the cage, and a zero-field-splitting parameter D=−2.6(4) MHz were determined. A persistent zero-field splitting is also observed in C 60 via the quartet spin of the encapsulated nitrogen, although no assignment of the director with respect to the molecular frame is possible. The observed line splitting is indicative of pseudo orientation of the rapidly rotating cage in this case.

Endohedral fullerenes $\mathrm{N}@{\mathrm{C}}_{60}$ and $\mathrm{N}@{\mathrm{C}}_{70}$ were dissolved in a liquid crystal and investigated by electron paramagnetic resonance. Sharp, liquid solution like spectra are observed. However, contrary to the usual solution spectra, the lines are split, indicating that the electron shell of the enclosed nitrogen atom is deformed and that an alignment with respect to the magnetic-field axis is achieved. The present results are of practical interest for controlling the interaction of endohedral fullerenes in a quantum computer.

In this article, the production and the properties of endohedral fullerenes N@C60, P@C60 and N@C70 are described. The distinct feature of these systems is that the enclosed nitrogen and phosphorous atoms keep their atomic ground state configuration and are localized in the center of the fullerenes. The atoms are almost freely suspended in these molecular cages and exhibit properties resembling those of ions in electromagnetic traps, i.e. sharp spectroscopic transitions and long life times. Since the fullerene shell can be easily manipulated, a large variety of different physical or chemical modifications can be realized.

Deuteron atoms encased in Silsesquioxane cages were used to detect deformations from the high temperature cubic cage symmetry. An analysis of the temperature dependence showed that the system undergoes a phase transition near 100 K changing the deformation from oblate to prolate (or vice versa). A theoretical study of the Hydrogen escape resulted in an escape barrier of 0.9 eV, close to the experimental value. Although the encased Deuterium atom exhibits an isotropic hyperfine coupling constant close to the free atom value, a spin population analysis revealed that approximately 10% of the spin density is transferred to the cage. In this respect the system falls some what short of the properties of an ideal cage, being defined by well decoupled atomic and molecular wave functions.

The EPR spectrum of radical anions of Sc3N@C80 is characterized by a very large isotropic Scandium hyperfine coupling constant (hfcc) (aiso=5.56 mT). The existence of three magnetically equivalent Sc nuclei indicates fast internal motion of the encased cluster. The large hfcc could indicate that not only significant spin transfer but also charge transfer from cage to cluster occurs upon reduction.

Fullerenes can act as inert cages for highly reactive nitrogen atoms even at room temperature. Confinement in a cage of less than spherical symmetry as realized in C70 leads to a characteristic deformation of the atomic charge and spin distributions which can be sensed by magnetic resonance techniques. A quantitative analysis of the amount of orbital squeezing is possible by comparison with data of free nitrogen ions.

Introducing an endohedral atom in one of the cages of the dimer opens the possibility to get information about changes in the electronic structure of the molecule due to polymerization. Nitrogen is known to form a stable endohedral fullerene and can be used for further chemical processing. In this contribution we will present first EPR results of the dimer being ‘doped’ with nitrogen in one of the cages. Zero Field Splitting induced by cage distortion is significantly larger than that found in the monoadduct (C2v-N@C61(COOCH2CH3)2).

Nitrogen in C60 is a paramagnetic atom with a magnetic moment corresponding to the S=3/2 electronic spin. The dipolar interaction of two N@C60 at closest distance, i.e. 1 nm apart, reaches a maximum value of 1.85 mT or 52 MHz, more than three times larger than the hyperfine interaction with the nuclear spin. For diluted N@C60 in a C60 matrix, the distribution of interactions leads to a line broadening in EPR experiments. We report here on a EPR line width measurement for N@C60 in C60 with concentrations varying by a factor of 1000. For the first time a concentration in the percent range was reached by repeated HPLC enrichment. A surprising and completely unexpected result is that sharp lines appear superimposed on the broad lines. We attribute the sharp line to motional narrowing of N@C60 diffusing on the surface of C60 grains. It can be assumed that the diffusion seen here is a general phenomenon of C60, the doped fullerene being just the indicator.

Ideal trapping behavior was recently discovered for nitrogen incased in C60 and C70, although significant increase of Fermi contact interaction gave evidence for compression of the atomic spin distribution. Fullerene cages therefor are candidates for the study of atomic orbital interaction with inert confinements. Prolate deformation of the spin and charge distribution of nitrogen in C70 was detected by high resolution ENDOR spectroscopy. Magnetic shielding averaged over the extended electronic orbitals in poly anions of fullerenes was found to be similar but not identical to the values measured for helium atoms at the cage center of the cages.

Dilute solutions of anion radicals produced from enriched endohedral N@C60 and N@C70 samples were prepared by reduction with lithium in tetrahydrofuran (THF). EPR spectra were measured at room temperature with a Bruker X-Band spectrometer. Although EPR signals from mono- to penta-anions of empty fullerenes gave characteristic signals, no signals could be detected for these reduction states originating from endohedral nitrogen. We believe that increased spin relaxation rates of states of higher spin multiplicity cause a line broadening impeding detection. Continuing reduction finally resulted in the diamagnetic hexaanions, detected by vanishing EPR signals of empty fullerenes and a reappearance of the characteristic three line spectrum of endofullerenes. The chemical shift was quite similar to those measured by the point-like 3He.

The “high spin” state of Nitrogen and Phosphorus atoms encapsulated in Fullerenes by ion bombardment provides a sensitive tool to test the symmetry of the local electric potential via Zero-Field-Splitting (ZFS) interaction. Because of the symmetry-dictated absence of this interaction in case of isolated C60, even small effects resulting for instance by collision-induced cage distortions or by long range ordering in the crystalline phase can be detected. As an example we studied the first-order phase transition of C60 at 258 K, by which the site symmetry at the Nitrogen position is lowered from Th to S6, thus allowing for the existence of ZFS with axial symmetry in the low temperature phase. Furthermore, the ability to detect the presence of trace amounts of paramagnetic species via fluctuating magnetic dipole-dipole interaction is also demonstrated.

The release of atomic nitrogen from fullerene cages under irradiation with ultraviolet laserlight has been studied. The experiments show that there is a more favorable decay pathway for N@C60 than for N@C70, indicating that the lifetime of the metastable triplet state is not controlling the escape.

Atomic Nitrogen and Phosphorus can be encapsulated in fullerenes acting as highly stable chemical traps. In solution, the neutral atoms in their quartet spin ground state are weakly coupled to the surrounding by zero-field-splitting interaction, resulting either from collision-induced deformations of the fullerene cage or by intrinsic deviations from spherical symmetry. From an analysis of the spin relaxation times, values for the correlation time and the mean square value of the interaction can be deduced.

Atomic Nitrogen in its quartet ground state can be encapsulated in C60 and its derivatives of reduced symmetry. Three endohedral fullerenes were studied in solid matrices for a determination of the permanent zero-field-splitting tensors. In solution the lowering of the site symmetry by collision-induced deformations of the fullerene cage apparently leads to a time dependent zero-field-splitting of the quartet spin state. The variance of the zero-field-splitting and the correlation time of this interaction are estimated from the absolute values of T1 and T2.

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Single-wall carbon nanotubes (SWNT) prepared by the "super growth" method developed recently exhibit electron paramagnetic resonance (EPR) signals, which can be attributed to itinerant spins. EPR results indicate very low defect and catalyst concentrations in this superior material. Under these conditions EPR can be used to study details of charge transport properties over a wide temperature range, although the material is still very "heterogeneous" with respect to tube diameter and chirality. Non-resonant microwave absorption in the temperature range below 20 K is indicative for the opening of a small gap at the Fermi energy for tubes of metallic character, which is indicative for a transition into a superconducting state. Using SWNT filled partially with an endohedral spin probe like N@C(60), such "peapods" can be investigated "from the inside". Continuous-wave (cw) and pulsed EPR was used to investigate localization dynamics within the tubes or to check for interaction with itinerant electrons. Using SWNT grown by different methods, the dominant influence of tube diameter on fullerene dynamics was revealed by temperature dependent pulsed EPR experiments. These differences can be correlated with the interactions between the endohedral observer spin and spins on the SWNT.

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Using multi-step high performance liquid chromatography (HPLC) it was possible to prepare a chromatographically pure sample of N@C60. Invoking EPR spectroscopy of solid samples prepared after each HPLC step, the increase of relative N@C60 concentration could unambiguously be determined. The UV/Vis spectrum of N@C60 is indistinguishable within experimental error from that of C60, confirming negligible coupling between nitrogen in its atomic ground state and C60 cage molecular wave functions. The observed large dipolar width of the EPR spectrum of the pure paramagnetic compound indicates weak spin exchange between neighboring paramagnetic centers which is further proof for a very small spin transfer from the encapsulated atom to the fullerene cage.

Evaluating the temperature dependent line broadening of paramagnetic spins on the surface of superconductors in the model of an ideal vortex state, an upper limit for λ∥

Using a fully deuterated sample of benzophenone, optically detected ENDOR transitions reveal line splittings due to deuterium quadrupole interaction in the excited triplet state. The line splittings were used to determine the ring-carbonyl-ring bond angle 2θ = 138(1.5)° and the phenyl-ring twist ansle ψ = 28.5(1.5)° of benzophenone in its metastable excited state.