Multiplet Components Research Articles

Determination of theβparameter for atomic Mn and Cr2pphotoemission: A benchmark test for core-electron photoionization theories

We have determined the anisotropy parameter $\ensuremath{\beta}$ for the electron angular distribution in direct $2p$ photoionization of free Mn and Cr atoms. By using a high-resolution electron spectrometer and by rotating the polarization axis of the linearly polarized synchrotron radiation the values for $\ensuremath{\beta}$ could be derived with high precision and separately for the different multiplet components. Combination of the experimental results with Hartree-Fock based single configuration and multiconfiguration ab initio calculations gives new insight into the atomic $3d$-metal $2p$ photoionization process. Configuration interaction in the final ionic states need to be taken into account to adequately describe the measured photoelectron angular distributions.

JE-TROSY: combined J- and TROSY-spectroscopy for the measurement of one-bond couplings in macromolecules

With the application of RDCs in high-resolution NMR studies of macromolecules, there has been an interest in the development of accurate, sensitive methods for measuring 15 N – 1 H and 13 C – 1 H one-bond coupling constants. Most methods for determining these couplings are based on the measurement of the displacement between cross-peak components in J-coupled spectra. However, for large macromolecules and macromolecular complexes, these methods are often unreliable since differential relaxation can significantly broaden one of the multiplet components (i.e., the anti-TROSY component) and thereby make accurate determination of its position difficult. To overcome this problem, a J-evolved transverse relaxation optimized (JE-TROSY) method is presented for the determination of one-bond couplings that involves J-evolution of the sharpest cross-peak multiplet component selected in a TROSY experiment. Couplings are measured from the displacement of the TROSY component in the additional J-evolution dimension relative to a zero frequency origin. The JE-TROSY method is demonstrated on uniformly labeled 15 N , 13 C -labeled RNA and peptide samples, as well as with an RNA–protein complex, in which the protein is uniformly 15 N , 13 C -labeled. In all cases, resolved, sensitive spectra are obtained from which heteronuclear one-bond J-couplings could be accurately and easily measured.

Spin-state effects on the outer core-level multiplet structures for high-spin Mn molecular clusters

Oxo-bridged manganese polynuclear complexes have applications in a variety of technologies, such as single-molecule nanomagnets, catalysis, and photosynthetic redox chemistry. X-ray photoemission spectroscopy was used to study the Mn 3p, 3s, and valence band electronic behavior as a function of Mn cluster structural properties, where the cluster size and nuclearity are systematically varied. Results show a chemical shift of the Mn 3p3/2,1/2 spin–orbit pair related to the cluster size and nuclearity. In addition, the Mn 3s S7 and S5 final state multiplet components shift since they involve the binding energy of a ligand valence electron. In addition, the branching ratio of the S7:S5 states is related to the 3s–3d electron correlation. Specifically, in the S7 state, the remaining 3s electron is well correlated with 3d electrons of parallel spin, while in the S5 state, the two spins are antiparallel. Changes in this electron correlation are clearly observed in the S7:S5 branching ratio as a function of cluster size and ligand electronegativity.

A theoretical study about the chirped pulse amplification laser

Starting from the Maxwell's equation and using the resonant-dipole equation together with the multilevel rate equations which take the effects of energy relaxation into consideration, we have derived a more realistic numerical model of the chirped pulse amplification for an ultra-broad band width laser amplifier. Numerical simulations of this model show that both the intensity profile and the energy fluence of the amplified chirped pulse are closely connected with the two relaxation effects: the relaxation of the thermalization among the components of the laser multiplets and the depletion of the lower laser level. The results are valuable for the design of ultra-broad bandwidth chirped pulse amplification lasers.

Measurement of methyl 13C-1H cross-correlation in uniformly 13C-, 15N-, labeled proteins.

An understanding of side chain motions in protein is of great interest since side chains often play an important role in protein folding and intermolecular interactions. A novel method for measuring the dynamics of methyl groups in uniformly 13C-, 15N-labeled proteins has been developed by our group. The method relies on the difference in peak intensities of 13C quartet components of methyl groups, in a spectrum recording the free evolution of 13C under proton coupling in a constant-time period. Cross-correlated relaxation rates between 13C-1H dipoles can be easily measured from the intensities of the multiplet components. The degree of the methyl restrictions (S(' 2)) can be estimated from the cross-correlated relaxation rate. The method is demonstrated on a sample of human fatty acid binding protein in the absence of fatty acid. We obtained relaxation data for 33 out of 46 residues having methyl groups in apo-IFABP. It has been found that the magnitude of the CSA tensor of spin 13C in a methyl group could be estimated from the intensities of the 13C multiplet components.

Observation of H-bond mediated 3hJH2H3 coupling constants across Watson-Crick AU base pairs in RNA.

3hJH2H3 trans-hydrogen bond scalar coupling constants have been observed for the first time in Watson-Crick AU base pairs in uniformly 15N-labeled RNA oligonucleotides using a new 2hJNN-HNN-E. COSY experiment. The experiment utilizes adenosine H2 (AH2) for original polarization and detection, while employing 2hJNN couplings for coherence transfer across the hydrogen bonds (H-bonds). The H3 protons of uracil bases are unperturbed throughout the experiment so that these protons appear as passive spins in E. COSY patterns. 3hJH2H3 coupling constants can therefore be accurately measured in the acquisition dimension from the displacement of the E. COSY multiplet components, which are separated by the relatively large 1JH3N3 coupling constants in the indirect dimension of the two-dimensional experiment. The 3hJH2H3 scalar coupling constants determined for AU base pairs in the two RNA hairpins examined here have been found to be positive and range in magnitude up to 1.8 Hz. Using a molecular fragment representation of an AU base pair, density functional theory/finite field perturbation theory (DFT/FPT) methods have been applied to attempt to predict the relative contributions of H-bond length and angular geometry to the magnitude of 3hJH2H3 coupling constants. Although the DFT/FPT calculations did not reproduce the full range of magnitude observed experimentally for the 3hJH2H3 coupling constants, the calculations do predict the correct sign and general trends in variation in size of these coupling constants. The calculations suggest that the magnitude of the coupling constants depends largely on H-bond length, but can also vary with differences in base pair geometry. The dependency of the 3hJH2H3 coupling constant on H-bond strength and geometry makes it a new probe for defining base pairs in NMR studies of nucleic acids.

Broadening of Er3+ electronic states in phosphate glasses

Absorption and emission spectra of Er3+-doped and Er3+–Yb3+-codoped phosphate glasses have been studied within the temperature interval from 10 to 300 K. The analysis of Er3+ Stark splitting for the excited state I13/24 and the ground-state I15/24 multiplets is performed. Simulation of inhomogeneous broadening of Stark levels has shown that all (2J+1) components of both multiplets are split by random distortions of the initial symmetric polyhedron, consisting of the neighboring oxygen ions in phosphate glasses. Inhomogeneous broadening of Stark levels is different for each energy level and reflects the sensitivity of a particular energy level to the variation of crystal field. At least three energy levels participate in shaping the low-energy side of the emission spectra, caused by the I13/24→I15/24 transition. The emission linewidth corresponding to the transition to the highest by energy Stark component is assumed to derive from comparable contributions of inhomogeneous and homogeneous broadening, the latter caused by intra-multiplet transitions. The presence of the highest Stark level in the crystal-field splitting of the ground-state I15/24 manifold with a high rate of nonradiative relaxation is essential for writing the rate equations which describe the laser operation of erbium glass lasers.

Line shape of the AgM4,5VVAuger spectra measured by Auger-photoelectron coincidence spectroscopy

We present high resolution Ag ${M}_{5}\mathrm{VV}$ and ${M}_{4}\mathrm{VV}$ Auger spectra obtained in coincidence with ${3d}_{5/2}$ and ${3d}_{3/2}$ core photoelectrons, respectively. Auger photoelectron coincidence spectroscopy (APECS) was used to separate these overlapping Auger lines and determine the intrinsic line shape of each spectrum. As the on-site Coulomb correlation energy U of Ag is comparable to twice the $4d$ bandwidth, $2W,$ (i.e., $U/2W\ensuremath{\sim}1),$ the coincidence Auger spectra exhibit both atomiclike and bandlike character. We find that whether considered separately or in combination, neither bandlike nor atomiclike line shapes give a satisfactory account of these Auger spectra. Instead, the intrinsic Ag ${M}_{5}\mathrm{VV}$ and ${M}_{4}\mathrm{VV}$ line shapes are well described by the Cini-Sawatzky theory when it is applied separately to each component of the multiplet structure of the ${4d}^{8}{5s}^{2}$ Auger final state. A fit to the APECS data indicates that the correlation energy the ${}^{1}{G}_{4}$ multiplet is $4.8\ifmmode\pm\else\textpm\fi{}0.1\mathrm{eV}.$ Furthermore, our analysis indicates that the missing intensity in the vicinity of the ${}^{3}{F}_{4}$ multiplet in the Ag ${M}_{5}\mathrm{VV}$ Auger line, which has been noted in previous studies, results from a shift in the spectral weight of this multiplet component to higher kinetic energy, into the bandlike region of the spectrum.

Radiative properties of Zeeman components of atomic multiplets: Magnetically induced decay of metastable 3 P 2 and 3 P 0 states of inert gases

It is shown that the magnetic field induces the radiative decay of metastable states of inert gases by mixing them with resonant sublevels of the lowest multiplet. The polarization and frequency structures of the “forbidden” lines induced by the magnetic field are determined, and the dependence of the intensity of π and σ components of these lines on the magnetic field is calculated. The effect is totally governed by the paramagnetic atom-field interaction, and the influence of the diamagnetic interaction is insignificant.

Multiplet component separation for measurement of methyl 13C-1H dipolar couplings in weakly aligned proteins.

A simple spectral editing procedure is described that generates separate subspectra for the methyl 13C-[1H3] multiplet components of 1H-13C HSQC spectra. The editing procedure relies on co-addition of in-phase and antiphase spectra and yields 1H-coupled constant-time HSQC subspectra for the methyl region that have the simplicity of the regular decoupled CT-HSQC spectrum. Resulting spectra permit rapid and reliable measurement of 1H-13C J and dipolar couplings. The editing procedure is illustrated for a Ca2+-calmodulin sample in isotropic and liquid crystalline phases.

High Spin Mn Molecular Clusters: Spin State Effects On the Outer Core-Level Multiplet Structures

AbstractOxo-bridged manganese polynuclear complexes have applications in a variety of technologies, such as single-molecule nanomagnets, catalysis and photosynthetic redox chemistry. The reason that these types of compounds are capable of such important and varied technologies is thought to be because they possess ground states with large spin values. However, the electronic, structural and magnetochemical relationships are not well understood and need to be thoroughly investigated to adequately explain why Mn is such an integral part of so many useful processes. X-ray photoemission spectroscopy was used to study the Mn 3p, 3s and valence band electronic behavior as a function of Mn cluster structural properties, where the cluster size and nuclearity are systematically varied. Results show a chemical shift of the Mn 3p3/2,1/2 spin-orbit pair related to the cluster size and nuclearity. Also, the Mn 3s 7S and 5S final state multiplet components shift since they involve the binding energy of a ligand valence electron. In addition, the branching ratio of the 7S:5S states is related to the 3s–3d electron correlation. Specifically, in the 7S state, the remaining 3s electron is well correlated with 3d electrons of parallel spin, while in the 5S state the two spins are antiparallel. Changes in this electron correlation are clearly observed in the 7S:5S branching ratio as a function of cluster size and ligand electronegativity.

Radiative properties of Zeeman components of atomic multiplets: Dependence of line intensities on the magnetic field

Analytical expressions for the dependence of the intensity of Zeeman components of doublet lines on the magnetic field are obtained. Sharp changes of these function on passing from the anomalous Zeeman effect to the Paschen-Back effect lead to the disappearance of marginal lines and the equalization of intensities of remaining lines. In the region of the complete Paschen-Back effect, a strong influence on these dependences is produced by the dynamic atom-field interaction, which weakens the paramagnetic effect in the states with a positive magnetic quantum number m and enhances the effect in the states with a negative m. Simple analytical expressions are obtained that take into account the effect of the diamagnetic interaction on line intensities. The role of the diamagnetic interaction increases in Rydberg atomic states with a large spin-orbit splitting. For the states with m > 0, it can lead to the “diamagnetic reversal” of the Paschen-Back effect, i.e., the recovery of the anomalous Zeeman effect.

Influence of a dense plasma on the fine-structure levels of a hydrogenic ion

We discuss the effects of plasma electron polarization surrounding a multiply charged hydrogenic impurity in a high density plasma on the fine-structure levels of the impurity ion. Calculations performed using the ion sphere model suggest that the magnitude of the fine-structure correction smoothly increases with increasing plasma electron density. The other features of the dense plasma effects include the removal of the k degeneracy of the Dirac levels, and a breakdown of the Z4 scaling of the fine-structure correction along the hydrogenic sequence of ions. The resultant outcome is a complete modification of the fine-structure multiplets in terms of the ordering and spacing between the multiplet components.

Clean TROSY: compensation for relaxation-induced artifacts.

TROSY pulse sequences for recording, e.g., (1)H-(15)N chemical shift correlation spectra of proteins are designed to select only one of four two-dimensional multiplet components. However, all of the variants published so far are prone to relaxation-induced artifacts at the positions of two of the other multiplet components. This article introduces modifications to the two spin-state-selective coherence transfer building blocks of the TROSY mixing sequence resulting in a clean TROSY spectrum with the artifacts largely suppressed. It works by having the new mixing sequence generate peaks of opposite phase at the positions of the relaxation artifacts. The clean TROSY pulse sequence is marginally shorter than the original one and contains the same pulses. Experimental demonstration is presented for the (15)N-labeled proteins RAP 17-97 (N-terminal domain of alpha(2)-macroglobulin receptor associated protein) and EQT, equinatoxin II, from the Mediterranean anemone Actinia equina.

Temperature dependence of the line shapes of two-photon excited transitions in KMgF3:Eu2+

The two-photon excitation line shapes of f-f transitions of Eu2+ in KMgF3 have been investigated as a function of temperature. Results for several transition lines of the 6P J and 6D J multiplets are presented in this work. The two-photon excited transitions appear as zero-phonon lines with a Lorentzian profile whose peak energy is shifted from the zero temperature position. The observed temperature dependence of the zero-phonon line shapes is ascribed to the elastic scattering of the electronic transitions among vibrational states via anharmonic coupling to a phonon mode of the lattice heat-bath. In those components of 4f7 multiplets whose energies are not resonant with the 4f65d broad excited state, a direct proportionality to the phonon occupation number of the coupled mode is found for the line-shapes and peak-positions temperature dependences.

Measurement of 1JNC′ and 2JHNC′ Couplings from Spin-State-Selective Two-Dimensional Correlation Spectrum

A method for the measurement of 1JNC′ and 2JHNC′ coupling constants from a simplified two-dimensional [15N, 1H] correlation spectrum is presented. The multiplet components of the 1JNC′ doublet in the indirect dimension and 2JHNC′ in the direct dimension are separated into two subspectra by spin-state-selective filters. Thus each subspectrum contains no more peaks than the conventional [15N, 1H]-HSQC spectrum. Furthermore, the method for the measurement of 1JNC′ and 2JHNC′ is designed to exploit destructive relaxation interference (TROSY). The results are verified against the measurements of 1JNC′ from spin-state-selective [13C′, 1H] correlation spectra recorded with additional sequence described here.

Improved sensitivity and coherence selection for [15N,1H]-TROSY elements in triple resonance experiments.

In experiments with proteins of molecular weights around 100 kDa the implementation of [15N,1H]-TROSY-elements in [15N]-constant-time triple resonance experiments yields sensitivity enhancements of one to two orders of magnitude. An additional gain of 10 to 20% may be obtained with the use of 'sensitivity enhancement elements'. This paper describes a novel sensitivity enhancement scheme which is based on concatenation of the 13C alpha-->15N magnetization transfer with the ST2-PT element, and which enables proper TROSY selection of the 15N multiplet components.

Measurement of 3hJNC' connectivities across hydrogen bonds in a 30 kDa protein.

A method is described which permits detection of 3hJNC' scalar couplings across hydrogen bonds in larger, perdeuterated proteins. The experiment is demonstrated for the uniformly 2H/13C/15N-enriched 30 kDa ribosome inactivating protein MAP30. The 3hJNC' interactions are smaller than 1 Hz, but their detection in an HNCO experiment is made possible through the use of constructive interference between the 15N chemical shift anisotropy and 1H-15N dipole-dipole relaxation mechanisms in a manner similar to that of recently proposed TROSY schemes. Sensitivity of the HNCO experiment depends strongly on the 15N transverse relaxation rate of the downfield 15N multiplet component and on the amide proton T1. In perdeuterated MAP30 at 40 degrees C, the average TROSY T2 was 169 ms at 750 MHz 1H frequency, and a wide range of longitudinal relaxation rates was observed for the amide protons.

Double spin-state-selective coherence transfer. Application for two-dimensional selection of multiplet components with long transverse relaxation times

The spin-state-selective coherence transfer (S3CT) pulse sequence element has earlier been introduced as a means of editing the two resonances of a doublet (Sørensen, M. D., et al. 1997, J. Biomol. NMR, 10, 181). This paper demonstrates how two consecutive S3CT elements in a mixing sequence can be used to edit the four multiplet components of a two-dimensional correlation cross peak of a two-spin system. A particular phase setting in the mixing sequence yields one component in the echo and one in the anti-echo part. However, since one of them passes through an intermediate state of zero-quantum coherence while the other passes through double-quantum coherence, a phase cycle or pulsed field gradients can separate the two. The resulting (S3CT)2 HSQC pulse sequence corresponds to transverse relaxation optimized spectroscopy (TROSY) (Pervushin, K., et al., 1997, Proc. Nat. Acad. Sci. USA, 94, 12366). Experimental confirmation is provided using a 15N-labelled protein, neural cell adhesion molecule (NCAM) modules 1 and 2, with a molecular weight of about 20kDa.

Double spin-state-selective coherence transfer. Application for twodimensional selection of multiplet components with long transverse relaxation times

Double spin-state-selective coherence transfer. Application for twodimensional selection of multiplet components with long transverse relaxation times