High-energy Modes Research Articles

Quantum phase transition and composite excitations of antiferromagnetic spin trimer chains in a magnetic field

Motivated by recent advancements in theoretical and experimental studies of the high-energy excitations on an antiferromagnetic trimer chain, we numerically investigate the quantum phase transition and composite dynamics in this system by applying a magnetic field. The numerical methods we used include the exact diagonalization, density matrix renormalization group, time-dependent variational principle, and cluster perturbation theory. From calculating the entanglement entropy, we have revealed the phase diagram which includes the XY-I, 1/3 magnetization plateau, XY-II, and ferromagnetic phases. Both the critical XY-I and XY-II phases are characterized by the conformal field theory with a central charge c ≃ 1. By analyzing the dynamic spin structure factor, we elucidate the distinct features of spin dynamics across different phases. In the regime with weak intertrimer interaction, we identify the intermediate-energy and high-energy modes in the XY-I and 1/3 magnetization plateau phases as internal trimer excitations, corresponding to the propagating of doublons and quartons, respectively. Notably, applying a magnetic field splits the high-energy spectrum into two branches, labeled as the upper quarton and lower quarton. Furthermore, we explore the spin dynamics of a frustrated trimerized model closely related to the quantum magnet Na2Cu3Ge4O12. In the end, we extend our discuss on the possibility of the quarton Bose-Einstein condensation in the trimer systems. Our results are expected to be further verified through the inelastic neutron scattering and resonant inelastic X-ray scattering, and also provide valuable insights for exploring high-energy exotic excitations.

Photohole-induced strong σ−π scattering driven by out-of-plane phonons in graphene

A theoretical study of the phonon-induced linewidths of the occupied electronic bands and the electron-phonon coupling (EPC) constant in graphene is presented. We propose an approximation in the spirit of the rigid ion approximation which considerably simplifies calculations of the EPC in metallic systems. We apply a tight-binding approach for the electrons and a force-constant model for the phonons with parameters obtained from . A simple procedure is presented in order to estimate the influence of the graphene-substrate interaction on the phonon dispersion and thereby also on, e.g., the linewidths. The EPC is the strongest in the energy region where π and σ bands overlap. We find that the electron scattering is predominantly driven by the out-of-plane acoustic ZA and optical ZO phonon modes, while in general the high-energy optical phonon modes LO and TO are of secondary importance. Published by the American Physical Society 2024

Efficient photosensitized luminescence from Eu3+ in inert nanocrystals via ligand coordination

Abstract Luminescent lanthanide ions incorporated in sodium yttrium fluoride nanocrystals are promising as new luminescent materials in optoelectronics and bioimaging since the nonradiative transition is significantly suppressed due to the absence of high-energy vibrational modes. To prepare optically and electrically active nanocrystals, we explored organic ligands that allow efficient triplet energy transfer to Eu3+ incorporated into nanocrystals, resulting in an efficient photosensitization effect in colloidal solutions and films. Further, we applied these emitting nanocrystals to light-emitting devices and observed the electroluminescence.

The importance of long range Fe–Fe interactions in magnetically ordered 2D Fe0.2Ni0.8/Ni(001) and Fe0.3Ni0.7/Ni(001) alloy systems

We develop a theoretical approach to study the magnonic properties of the 2D ordered surface Fe–Ni alloys with 20% and 30% Fe on a face-centered cubic Ni(001) surface substrate. The surface alloy nanostructures in stable equilibrium are determined by computing the lowest energy configurations of constitutive supercells of the ordered alloys. The magnetic exchange constants of the ground state of the stable systems are calculated to define their Heisenberg Hamiltonians using the DFT Spin-Polarized Relativistic Korringa–Kohn–Rostoker (SPRKKR) method and considering Fe–Fe interactions up to third nearest neighbors. To determine the propagating exchange spin-wave modes, evanescent modes, and the consequent magnonic properties, the spin dynamics of the magnetic surface alloy nanostructures are solved using the phase field matching theory (PFMT). Our results indicate that the Fe–Fe exchange interactions up to third nearest neighbors are vital for accurately describing their magnonics. In particular, the exchange interactions influence the form of dispersion branches for the high-energy spin-wave modes of the Fe–Ni surface alloys considered. Appropriate Green’s functions are also derived from the PFMT method to compute the local densities of states (LDOS) for the atomic sites at the surface boundary. For the case of 20% Fe surface alloy, the Fe–Fe exchange interactions shift the Fe LDOS peaks to lower frequency intervals. We also distinguish the emergence of remarkable LDOS peaks for the he case of the 30% Fe surface alloy at specific Ni sites. These peaks change positions under second and third nearest neighbor Fe–Fe interactions, heralding new accessible spin-wave channels. Our results contribute to establishing a systematic understanding of the magnonics of the magnetic surface alloys of transition metal (TM) materials. This new knowledge will enable the study of the quantum transport of spin waves at interfacial alloy nanojunctions composed of such materials. The present DFT-PFMT theoretical approach is general and can be applied to other surface TM alloy magnetic nanostructures.

A Comparative Study of the Mode-Decomposed Characteristics of the Asymmetricity of a Vortex Rope with Flow Rate Variation

In hydro turbines, the draft tube vortex rope is one of the most crucial impact factors causing pressure pulsation and vibration. It is affected by operating conditions due to differences in the flow rate and state and can be symmetric or asymmetric along the rotational direction. It may influence the stability of draft tube flow. To achieve a better understanding, in this work, dynamic mode decomposition is used in a draft tube case study of a simplification of a vortex rope. As the flow rate increases, the shape of the vortex rope becomes clear, and the flow rotation becomes more significant as the inlet flow rate increases. Dynamic mode decomposition was used to determine the relative frequencies, which were 0 (averaged), 0.7 times, and 1.4 times the features of the reference frequency. As the inlet flow rate increases, the order of high-energy modes and their influence on the vortex rope gradually increase, and this characteristic is exhibited further downstream of the draft tube. When the inlet flow rate is low, the impact of mode noise is greater. As the flow velocity increases, the noise weakens and the rotation mode becomes more apparent. Identifying the mode of the vortex flow helps extract characteristics of the vortex rope flow under different operating conditions, providing a richer data-driven basis for an in-depth analysis of the impact of operating conditions on the flow stability of a draft tube.

Ultrastructural and glycoproteomic characterization of Prevotella intermedia: Insights into O-glycosylation and outer membrane vesicles.

Prevotella intermedia, a Gram-negative bacterium from the Bacteroidota phylum, is associated with periodontitis. Other species within this phylum are known to possess the general O-glycosylation system. The O-glycoproteome has been characterized in several species, including Tannerella forsythia, Porphyromonas gingivalis, and Flavobacterium johnsoniae. In our study, we used electron cryotomography (cryoET) and glycoproteomics to reveal the ultrastructure of P. intermedia and characterize its O-glycoproteome. Our cryoET analysis unveiled the ultrastructural details of the cell envelope and outer membrane vesicles (OMVs) of P. intermedia. We observed an electron-dense surface layer surrounding both cells and OMVs. The OMVs were often large (>200 nm) and presented two types, with lumens being either electron-dense or translucent. LC-MS/MS analyses of P. intermedia fractions led to the identification of 1655 proteins, which included 62 predicted T9SS cargo proteins. Within the glycoproteome, we identified 443 unique O-glycosylation sites within 224 glycoproteins. Interestingly, the O-glycosylation motif exhibited a broader range than reported in other species, with O-glycosylation found at D(S/T)(A/I/L/M/T/V/S/C/G/F/N/E/Q/D/P). We identified a single O-glycan with a delta mass of 1531.48 Da. Its sequence was determined by MS2 and MS3 analyses using both collision-induced dissociation and high-energy collisional dissociation fragmentation modes. After partial deglycosylation with trifluoromethanesulfonic acid, the O-glycan sequence was confirmed to be dHex-dHex-HexNAc (HPO3 -C6 H12 O5 )-dHex-Hex-HexA-Hex(dHex). Bioinformatic analyses predicted the localization of O-glycoproteins, with 73 periplasmic proteins, 53 inner membrane proteins, 52 lipoproteins, 26 outer membrane proteins, and 14 proteins secreted by the T9SS.

Highly uniform core/shell structures AuR/Ag and AuR/Ag@BSA with various shell thicknesses for surface-enhanced Raman scattering

This work indicates the synthesis of uniform core/shell nanostructures (AuR/Ag) with different thicknesses of Ag shell by the double seed method. This method consists of two self-sufficient progresses, one seed for the formation of gold nanorods (AuRs) and one for the formation of the Ag shell for the gold nanorods to form the AuR/Ag. Acid ascorbic (L-AA) acts as a weak reducing agent and hexadecyltrimethylammonium chloride (CTAC) acts as a surfactant for Ag shell. The formation and growth of the Ag shell were carefully investigated by changing the reaction factors such as temperature, time, and concentration of AgNO3. The greater the concentration of AgNO3 shelling precursor, the thicker the shell and therefore the more high-energy vibrational modes appear in the near-ultraviolet region. In survey of surface-enhanced Raman scattering effect of AuRs and AuR/Ag with Rhodamine B (RB) detector, the results show that AuR/Ag has the ability to enhance Raman signal much better than AuRs. At the same time, the thicker the Ag shell, the better the Raman signal enhancement ability.

Reduced Order Data-Driven Analysis of Cavitating Flow over Hydrofoil with Machine Learning

Predicting the flow situation of cavitation owing to its high-dimensional nonlinearity has posed great challenges. To address these challenges, this study presents a novel reduced order modeling (ROM) method to accurately analyze and predict cavitation flow fields under different conditions. The proposed ROM decomposes the flow field into linearized low-order modes while maintaining its accuracy and effectively reducing its dimensionality. Specifically, this study focuses on predicting cavitation on the Clark-Y hydrofoil using a combination of numerical simulation, proper orthogonal decomposition (POD), and neural networks. By analyzing different cavitation conditions, the results revealed that the POD method effectively reduces the order of the cavity flow field while achieving excellent flow field reconstruction. Notably, the zeroth- and first-order modes are associated with attachment cavitation, while the second-, third- and fourth-order modes correspond to cavitation shedding. Additionally, the fifth- and sixth-order modes along the hydrofoil surface are associated with the backward jet flow. To predict the conditions of high-energy modes, the neural network proved to be more effective, exhibiting excellent performance in stable attached cavitation. However, for cloud cavitation, the accuracy of the neural network model requires further improvement. This study not only introduces a novel approach for predicting cavitation flow fields but also highlights new challenges that will require continuous attention in future research endeavors.

Excited-state normal-mode analysis: The case of porphyrins.

We systematically applied excited-state normal mode analysis to investigate and compare the relaxation and internal conversion dynamics of a free-base porphyrin (BP) with those of a novel functional porphyrin (FP) derivative. We discuss the strengths and limitations of this method and employ it to predict very different dynamical behaviors of the two compounds and to clarify the role of high reorganization energy modes in driving the system toward critical regions of the potential energy landscape. We identify the modes of vibrations along which the energy gap between two excited-state potential energy surfaces within the Q band manifold may vanish and find that the excess energy to reach this "touching" region is significantly reduced in the case of FP (0.16eV) as compared to the one calculated for BP (0.92eV). Our findings establish a link between the chemical functionalization and the electronic and vibrational structure that can be exploited to control the internal conversion pathways in a systematic way.

Numerical and experimental studies of a morphing airfoil with trailing edge high-frequency flapping

The aerodynamic performance of a morphing airfoil is numerically and experimentally investigated. The morphing airfoil is designed based on macro fiber composites, capable of trailing edge flapping during 10–90 Hz with a maximum amplitude of 0.55 mm. A numerical model with flexible deformation walls based on the experiment is established to precisely restore the actual dynamic morphing instead of segmental deformation to explore the transient aerodynamic performance of high-frequency flapping. The drag coefficient is reduced by 2.07% at the flapping frequency (ff) of 37.5 Hz compared with the rigid airfoil, while the drag coefficient and the lift coefficient increase by 4.8% and 5.8% for ff at 600 Hz. The vortex is broken up by flapping, and the corresponding position has been forwarded to the tail. Dynamic mode decomposition shows that the wing's flapping dominates the second mode and the high-frequency vortex has changed to low-frequency. The energy of higher modes is transferred to lower-order modes that the first mode's power has risen sharply from 49.29% of the rigid airfoil to 91.83%. In the wind tunnel experiment, the lift and drag forces are increased by 1.88% and 0.77% at the flapping frequency of 40 Hz, respectively. Furthermore, the lift force frequency is locked by flapping and changes from 124.9 Hz of the rigid airfoil to the flapping frequency, consistent with the computational fluid dynamics results. The research has provided a solution to reduce the drag force and increase the lift force of the aircraft by the trailing edge flapping.

The tensor of the exact circle: reconstructing geometry

Developing a theory for quantum gravity is one of the big open questions in theoretical high-energy physics. Recently, a tensor model approach has been considered that treats tensors as the generators of commutative non-associative algebras, which might be an appropriate interpretation of the canonical tensor model. In this approach, the non-associative algebra is assumed to be a low-energy description of the so-called associative closure, which gives the full description of spacetime including the high-energy modes. In the previous work it has been shown how to (re)construct a topological space with a measure on it, and one of the prominent examples that was used to develop the framework was the exact circle. In this work we will further investigate this example, and show that it is possible to reconstruct the full Riemannian geometry by reconstructing the metric tensor. Furthermore, it is demonstrated how diffeomorphisms behave in this formalism, firstly by considering a specific class of diffeomorphisms of the circle, namely the ellipses, and subsequently by performing an explicit diffeomorphism to ‘smoothen’ sets of points generated by the tensor rank decomposition.

Raman Spectroscopic Study of Ruddlesden—Popper Tetragonal Sr2VO4

The lattice dynamics of tetragonal Sr2VO4 with a Ruddlesden—Popper-layered crystal structure was studied via Raman spectroscopy. We observed three of the four expected Raman-active modes under ambient conditions. Mode Grüneisen parameters and the implicit fractions of two A1g Raman-active modes were determined from high-pressure and high-temperature Raman spectroscopy experiments. The low-energy A1g Raman-active mode involving Sr motions along the c direction has a large isothermal Grüneisen parameter about seven times larger than that of the high-energy A1g Raman-active mode involving apical O motions along the c direction and is, therefore, more anharmonic. The thermodynamic Grüneisen parameter is significantly smaller in Sr2VO4 than in Sr2TiO4 due to the smaller Grüneisen parameter of the high-energy A1g Raman-active mode and other vibrational modes that still need to be identified. The explicit contribution of the low-energy A1g Raman-active mode is negative, and the implicit contribution due to volume change is much larger. Both volume implicit and anharmonic explicit contributions of the high-energy A1g Raman-active mode have similar positive values. The Raman experiment in the air shows that Sr2VO4 begins to decompose above 200 °C.

Data-driven reduced-order simulation of dam-break flows in a wetted channel with obstacles

Accurate and timely information on dam-break waves is essential for risk assessment and disaster mitigation. The unsteady flow interacting with in-channel obstacles renders numerical simulations computationally costly. This study establishes a machine learning (ML)-enhanced reduced-order model (ROM), which provides accelerated and accurate flow predictions. The model consists of three phases: dimensionality reduction, long short-term memory (LSTM) optimization and forecasting, and flow field reconstruction. The proper orthogonal decomposition (POD) first reduces the complexity of the physical system while maintaining the dominant flow dynamics. Subsequently, an LSTM fine-tuned by the grey wolf optimization (GWO) predicts the evolution of the POD coefficients in the reduced-order space. Lastly, the flow field is reconstructed using the high-energy POD modes and the estimated amplitudes. The proposed GWO-LSTM-ROM is evaluated for time-dependent dam-break flows in a wetted channel with obstacles. Based on the comparison of millions of data samples, the approach is highly consistent with the high-fidelity full-order model, with a coefficient of determination over 0.99. Meanwhile, the average computational efficiency is improved by 86%. The main contribution of this work is to develop an improved method for fast and accurate modeling of complex flows, benefiting a wide range of applications, e.g., multiphase flows and fluid-structure interactions.

Modeling Surface Vibrations and Their Role in Molecular Adsorption: A Generalized Langevin Approach.

The atomic vibrations of a solid surface can play a significant role in the reactions of surface-bound molecules, as well as their adsorption and desorption. Relevant phonon modes can involve the collective motion of atoms over a wide array of length scales. In this paper, we demonstrate how the generalized Langevin equation can be utilized to describe these collective motions weighted by their coupling to individual sites. Our approach builds upon the generalized Langevin oscillator (GLO) model originally developed by Tully. We extend the GLO by deriving parameters from atomistic simulation data. We apply this approach to study the memory kernel of a model platinum surface and demonstrate that the memory kernel has a bimodal form due to coupling to both low-energy acoustic modes and high-energy modes near the Debye frequency. The same bimodal form was observed across a wide variety of solids of different elemental compositions, surface structures, and solvation states. By studying how these dominant modes depend on the simulation size, we argue that the acoustic modes are frozen in the limit of macroscopic lattices. By simulating periodically replicated slabs of various sizes, we quantify the influence of phonon confinement effects in the memory kernel and their concomitant effect on simulated sticking coefficients.

On the surface flow patterns and associated aerodynamics of an asymmetrical flat-box section

In this study, wind tunnel experiments were carried out in smooth flow to examine the nexus between flow patterns around a flat-box section and its aerodynamics with the variation of the wind angle of incidence (α). The model cross section closely represents the overall asymmetric geometry and attendant aerodynamics of a class of flat-box decks frequently employed in long-span bridges. To explore the flow around and associated aerodynamic properties of this model that are distinct from a typical symmetric section (e.g., rectangular), detailed wind tunnel tests involving smoke-wire based flow visualizations and synchronous multipoint pressure measurements were carried out. Experimental results were analyzed to identify flow patterns, pressure distributions and associated Strouhal numbers, power spectral densities, aerodynamic force coefficients, proper orthogonal decomposition (POD) analyses, and span-wise correlation. Three typical flow patterns previously observed around symmetric bluff bodies with varying α were also observed in the asymmetric cross section, i.e., the trailing-edge vortex shedding (TEVS), the impinging leading-edge vortices (ILEV), and the alternate-edge vortex shedding (AEVS). However, due to the chordwise asymmetry of the section, the three flow patterns identified are distinct from the classical ones associated with symmetric sections in terms of flow separation points, the static “stall” angle of the section, and characteristics of leading-edge vortices. The roles played by these flow patterns in the aerodynamics of the flat-box section have been identified. It is observed that, if the ILEV or AEVS governs the flow topology, the aerodynamic force coefficients vary nonlinearly with the increase in α, in contrast with the linear variation in the TEVS-dominant case. For cases in which the TEVS dominates, the POD mode participation factors of the fluctuating pressure field display energy in higher modes. In this case, the reconstruction process requires that higher POD modes are retained. Finally, in the TEVS flow pattern, a weaker spanwise correlation of the fluctuating forces is noted as compared to the ILEV and AEVS-type flows. This study is limited to the fundamental examination of asymmetric section aerodynamics in smooth flows, which should be extended in case the influences of turbulence and aeroelastic effect are of interest.

Infrared and Raman spectroscopy investigations in mullite-type Bi2(FexGa1-x)4O9 polycrystals

Mullite-type Bi2(FexGa1-x)4O9 (0 ≤ x ≤ 1) oxides, prepared by mecanochemical-thermal synthesis, were investigated by FTIR and Raman spectroscopies. Similarly to other mullite systems, IR (850–400 cm−1) and Raman bands (750–300 cm−1) are attributed to stretching and bending vibrations of tetrahedral and octahedral sites. A shift in the peak positions toward lower wavenumbers with the increase of iron content is observed. High-energy IR modes show only the presence of Ga-O-Ga and Ga-O-Fe/Fe-O-Ga stretching vibrations for x < 0.5. Raman bands between 500 cm−1 and 400 cm−1 revealed double band splitting for x < 0.5.

Structural modal identification and enhancement of low-energy modes by successively variational extraction of high-energy modes

Accurate identification of modal properties for as much as possible modes from structural monitoring responses is an important part for structural health monitoring systems. Limited by the energy of external excitations, or influenced by the heavy noise, the energies of some modal components may be weak or buried in the energy of noise, giving rise to the difficulty for accurate modal identification. Variational mode decomposition method is a non-recursive decomposing procedure to decompose a signal into narrow-band sub-components. However, the difficulty for the decomposition of low-energy mode is determining the corresponding initial center frequencies. In this study, a new method for low-energy mode identification is proposed using the idea of locating, identifying, and subtracting the high-energy component to gradually enlarge the relative energy level of low-energy mode by substituting the original signal with residual signal repeatedly. First, the initial center frequency of the mode with maximum energy is determined by autoregressive power spectrum; second, the modal parameters including frequency, damping ratio and mode shape are identified by the singular value decomposition of Hankel matrix with low system order; third, vibrational mode extraction method is proposed to extract the modal component with maximum energy; subsequently, the modal component with maximum energy is subtracted from the original signal to construct the residual signal for the identification of next maximum energy component. The relative energy level of low-energy mode is enlarged gradually by repeating the subtraction of high-energy modal component. Then, the accuracy of low-energy mode identification is improved. The effectiveness of the proposed method is verified by the simulated structures under ambient and earthquake excitations with high-level noises. Besides, the capability for the application of practical structure is verified by the experimental data of a real bridge.

In hot pursuit of a stable wormhole in beyond Horndeski theory

We consider the issue of stability at the linearized level for static, spherically symmetric wormhole solutions within a subclass of scalar-tensor theories of beyond Horndeski type. In this class of theories we derive a set of stability conditions ensuring the absence of ghosts and both radial and angular gradient instabilities about a static, spherically symmetric background. This set of constraints extends the existing one and completes the stability analysis for high energy modes in both parity odd and parity even sectors, while ``slow'' tachyonic instabilities remain unconstrained. We give an example of beyond Horndeski Lagrangian admitting a wormhole solution which complies with all stability constraints for the high energy modes.

Caging of vibrational energy transfer and interactions in binary mixed solvents probed from Raman scattering linewidth

The research focuses on Raman effects from vibrational interactions for mixed solute and solvent in binary mixed liquid for vibrational exchange from anharmonic interactions from three and four body collisions of mixed solvents from shields and cages about excited molecule of solute. The Raman linewidth were measured and theoretically fitted by varying the mole fraction (X) of solute proportions with mixed solvents, one acting as a solute and the other as a solvent. The excitation of CH3 modes to the daughter modes and other mixed molecule modes show the effect of anharmonic many body collisions, dephasing and vibrational energy transfer. The Raman linewidth and intensity of the higher vibrational modes of solvents: Acetone and Methanol can rise in the presence of a second solvent of lower vibrational modes act as shield. Using various combinations of the solvents as acetone and methanol with carbon disulfide, and carbon tetrachloride can alter relaxation pathways due to the interruption of intermolecular energy decay routes of acetone and methanol by the low energy modes of carbon tetrachloride and carbon disulfide act as shields to energy transfer. Carbon tetrachloride is a stronger shielding agent than carbon disulfide for both acetone’s high and low energy modes due to acetone’s larger amphiphilic structure that is more resilient to structural hindrance of the linear carbon disulfide as opposed to the larger spherical carbon tetrachloride. Carbon disulfide is a stronger shielding agent than carbon tetrachloride for methanol except in the case of 1456 cm−1 energy mode due to the increased structural hindrance of carbon disulfide’s linear structure, which methanol is more susceptible to by its smaller molecular structure, preventing intermolecular interactions with other methanol molecules.

High-Resolution Photoelectron Spectroscopy of Vibrationally Excited Vinoxide Anions.

High-resolution photoelectron spectra of vibrationally pre-excited vinoxide anions (CH2CHO-) are reported using the recently developed IR-cryo-SEVI technique. This method is combined with a newly developed implementation of vibrational perturbation theory that can readily identify relevant anharmonic couplings among nearly degenerate vibrational states. IR-cryo-SEVI spectra are obtained by resonant infrared excitation of vinoxide anions via the fundamental C-O (ν4, 1566 cm-1) or isolated C-H (ν3, 2540 cm-1) stretching vibrations prior to photodetachment. Excitation of the ν4 mode leads to a well-resolved photoelectron spectrum that is in excellent agreement with a harmonic Franck-Condon simulation. Excitation of the higher-energy ν3 mode results in a more complicated spectrum that requires consideration of the calculated anharmonic resonances in both the anion and the neutral. From this analysis, information about the zeroth-order states that contribute to the nominal ν3 wave function in the anion is obtained. In the neutral, we observe anharmonic splitting of the ν3 fundamental into a polyad feature with peaks at 2737(22), 2 835(18), and 2910(12) cm-1, for which only the center frequency has been previously reported. Overall, 9 of the 12 fundamental frequencies of the vinoxy radical are extracted from the IR-cryo-SEVI and ground-state cryo-SEVI spectra, most of which are consistent with previous measurements. However, we provide a new estimate of the ν5 (CH2 scissoring) fundamental frequency at 1395(11) cm-1 and attribute the discrepancy with previously reported values to a Fermi resonance with the 2ν11 overtone (CH2 wagging).