Vibrational Energy States Research Articles

Influence of Packing on Low Energy Vibrations of Densified Glasses

A comparative study of Raman scattering and low temperature specific heat capacity has been performed on samples of B2O3, which have been high-pressure quenched to go through different glassy phases having growing density to the crystalline state. It has revealed that the excess volume characterizing the glassy networks favors the formation of specific glassy structural units, the boroxol rings, which produce the boson peak, a broad band of low energy vibrational states. The decrease of boroxol rings with increasing pressure of synthesis is associated with the progressive depression of the excess low energy vibrations until their full disappearance in the crystalline phase, where the rings are missing. These observations prove that the additional soft vibrations in glasses arise from specific units whose formation is made possible by the poor atomic packing of the network.

Evaluation of theoretical functionals for structural and vibrational energy predictions on organo-rhenium(VII) oxides

The crystal structure of xylyltrioxorhenium has been determined and the applicability of the hybrid density functionals B3LYP, O3LYP, M06 and the gradient-corrected PBEPBE functional for predicting ground state geometries and vibrational energies of selected alkyl- and aryl Re(VII) trioxo compounds were evaluated. Different combinations of ECPs and basis sets (Stuttgart/Dresden 1997, LANL2DZ/LANL2TZ, 6-31G(d), 6-311 + G(d,p)) were examined. A combination of the split valence triple-ζ basis set 6-311 + G(d,p) with LANL2ZZ and O3LYP provided to be most appropriate, while BPEBPE produced inferior results.

Imaging of Living Embryos

AbstractMultiphoton Microscopy is an advanced imaging technique for biological material that differs from standard confocal approaches. Multiphoton systems are the preferred choice for living, cellular imaging as it utilizes longer infrared wavelengths for excitation as opposed to shorter UV blue wavelengths that are more harmful to cellular tissue. This is done by taking advantage of the vibrational energy states of living tissue and results in an emission signal that is shorter than the excitation wavelengths. Multiphoton microscopy does not have the level of resolution that confocal microscopy has, but users are able to image deeper into living specimens which is extremely beneficial for non‐invasive biopsies performed in vivo. One application that truly demonstrates the benefits and differences between the two techniques is the imaging and analysis of living embryos.

The vibrational bound states of isomerising disilyne

Full-dimensional variational calculations are reported for the isomerising disilyne molecule, Si2H2. Large-scale calculations using coordinates based on orthogonal satellite vectors permitted the computation of excited vibrational state energies and wavefunctions for all four isomeric forms: dibridged Si(H2)Si, monobridged Si(H)SiH, disilavinylidene H2SiSi, and trans-bent HSiSiH. Energies and wavefunctions have been determined for the lowest 2400 totally symmetric vibrational states; this set includes highly excited states above all three chemically relevant isomerisation barriers--up to about 8300 cm(-1) above the (dibridged) ground state. States strongly localised in the dibridged, monobridged, and disilavinylidene regions of the potential energy surface have been found as well as many partially or fully delocalised states. For the trans-bent form, only partially localised states have been identified. Comparisons are made with similar literature calculations on the isovalent acetylene-vinylidene system HCCH/H2CC.

Progress in vibrational spectroscopy in diagnosis and screening

Vibrational spectroscopy has a great potential in diagnosis and screening with increasing number of applications in biological and biomedical fields, food and environmental sciences and forensic area. This review focuses on the historical background and recent developments related to the use of this technique in various areas of diagnosis and screening. Vibrational spectroscopy consists of some of the oldest methods that are used in the analysis of sam- ples. William Herschel discovered the infrared region of electromagnetic radiation in 1800 (2). Before that, the strength of infrared spectroscopy for structural characterization of molecules was known and it was admitted as a significant method to analyse the structure of biological molecules in addition to X-ray diffraction. and terahertz (THz) spectroscopy are the other currently used vibrational spectroscopic tech- niques to understand structure and composition of biological samples. The basic theory of the Raman effect was developed by Chandrasekhara Venkata in 1928 (29), while THz spectroscopy was discovered in 1988 (33). All of these techniques based on the transitions between vibrational energy levels of molecules as a result of absorbtion of electromagnetic radiation. The region between 14,000 and 4c m −1 of the electromagnetic radiation is called as infrared region which is divided into three sub- regions as near-infrared region (14,000 to 4,000 cm −1 ), mid-infrared region (4,000 to 400 cm −1 )a nd far-infrared region (400 cm −1 to 4c m −1 ). However, the THz spectral region from 10 THz (333 cm −1 ) − 1t o 0.06 THz (2 cm −1 ) has generally been used in biophysics and biochemistry. In spec- troscopy, transition between vibrational energy levels is induced by ultraviolet (UV), visible (VIS) or NIR. According to the quantum theory, this is a low probability event, because incident radiation does not match the energy differences between vibrational energy states that are used in spectroscopy. In spectroscopy, a small amount of energy of an incident photon can be transfered to one of the molecules that causes transition of molecule to the higher vibrational state. The energy lost of the incident photon is equal to the energy of a transition from one vibrational state to another. Since a

Accurate and efficient calculation of excited vibrational states from quartic potential energy surfaces

Vibrational anharmonicity and resonances frequently complicate assignment of vibrational spectra. In order to analyse such spectra, these effects can be calculated from ab initio quartic potential energy surfaces (PESs) using second-order vibrational theory with resonances (VPT2 + K). This study compares the accuracies of using the cc-pVTZ basis set, the aug-cc-pVQZ basis set, and a hybrid approach that uses the cc-pVTZ basis set for the equilibrium geometry and quadratic force constants and the aug-cc-pVQZ basis set for the cubic and quartic force constants. Quartic PESs are computed using these basis sets for H2O, H2CO, HFCO, SCCl2, and their deuterated analogs with the CCSD(T) method. The computed PESs are assessed by comparing experimentally determined and theoretically calculated spectroscopic constants. The average absolute difference (⟨|error|⟩) between theoretical and experimental zero-point energy-corrected harmonic frequencies () decreases by 54.7% when the hybrid approach is used instead of the cc-pVTZ basis, but decreases by only an additional 2.3% when the aug-cc-pVQZ basis is used. The computed PESs are also assessed by comparing predicted and observed vibrational energy states. The weighted average root-mean-square (RMS) difference between predicted and observed vibrational energy levels decreases by 42.3% when the hybrid approach is used instead of cc-pVTZ, but decreases by only an additional 4.0% when aug-cc-pVQZ is used. These results demonstrate that calculations performed using the hybrid basis set approach, which have a substantially lower computational cost, are comparable in accuracy to those performed using the aug-cc-pVQZ basis set.

Anharmonic Frequencies of CX2Y2 (X, Y = O, N, F, H, D) Isomers and Related Systems Obtained from Vibrational Multiconfiguration Self-Consistent Field Theory

Accurate anharmonic frequencies are provided for molecules of current research, i.e., diazirines, diazomethane, the corresponding fluorinated and deuterated compounds, their dioxygen analogs, and others. Vibrational-state energies were obtained from state-specific vibrational multiconfiguration self-consistent field theory (VMCSCF) based on multilevel potential energy surfaces (PES) generated from explicitly correlated coupled cluster, CCSD(T)-F12a, and double-hybrid density functional calculations, B2PLYP. To accelerate the vibrational structure calculations, a configuration selection scheme as well as a polynomial representation of the PES have been exploited. Because experimental data are scarce for these systems, many calculated frequencies of this study are predictions and may guide experiments to come.

Effect of diatomic molecular properties on binary laser pulse optimizations of quantum gate operations

The importance of the ro-vibrational state energies on the ability to produce high fidelity binary shaped laser pulses for quantum logic gates is investigated. The single frequency 2-qubit ACNOT(1) and double frequency 2-qubit NOT(2) quantum gates are used as test cases to examine this behaviour. A range of diatomics is sampled. The laser pulses are optimized using a genetic algorithm for binary (two amplitude and two phase parameter) variation on a discretized frequency spectrum. The resulting trends in the fidelities were attributed to the intrinsic molecular properties and not the choice of method: a discretized frequency spectrum with genetic algorithm optimization. This is verified by using other common laser pulse optimization methods (including iterative optimal control theory), which result in the same qualitative trends in fidelity. The results differ from other studies that used vibrational state energies only. Moreover, appropriate choice of diatomic (relative ro-vibrational state arrangement) is critical for producing high fidelity optimized quantum logic gates. It is also suggested that global phase alignment imposes a significant restriction on obtaining high fidelity regions within the parameter search space. Overall, this indicates a complexity in the ability to provide appropriate binary laser pulse control of diatomics for molecular quantum computing.

Laser remote sensing: yesterday, today and tomorrow

Development of laser remote sensing (lidar echniques) is discussed for atmosphere and ocean investigation. Examples of Raman lidars based on vibrational and rotational energy states of molecular species are demonstrated for remote detection and monitoring of pollution, as well as for studies of dynamics of different components and their parameters. Coherent laser radars allowed remote measurement of speed and vibrations, Doppler velocity information being crucial for the solution of the problem of windshear detection and flight security. A promising trend in laser radar development is incorporation of range and velocity data into the image information. Gated imaging, as one of the 3D techniques, demonstrated its prospects (looking through scattering media, vegetation, dress, etc.) for military and civilian use.

Multiphoton dissociation and vibrational mediated dissociation of chlorinated methanes, CH 4− nCl n ( n = 2, 3, 4) at 355 nm

In this paper, the experimental results for the photodissociation, PD, and photoionization, PI, of chlorinated methanes, CH 2Cl 2, CHCl 3, and CCl 4, studied by cooled molecular jets and Time of Fly Mass Spectrometry detection, ToF-MS, are presented. Photodissociation processes outcome from multiphoton absorption at 10 9–10 10 W cm −2 intensities at 355 nm laser radiation. The results indicated that photodissociation dominates over photoionization processes as some detected ions are originated from the absorption of up to five photons. The main dissociative channels lead to the formation of H +, C +, CH +, CH 2 +, 35Cl +, 37Cl +, C 35Cl +, and C 37Cl +. The analysis of the ratio of ion yield from different isotopologues for each molecule, as a function of the energy per pulse, showed that the formation of the more abundant ions: Cl + and CCl +, is strongly influenced by changes in the vibrational structure of the excited states as a consequence of the two different stable chlorine atoms. As a first approach to get some insight of the experimental results, the ground state vibrational energy levels for chlorinated methanes, were calculated using Density Functional Theory. From the abovementioned calculations was possible to think that the changes in energy of the vibrational levels drive the ion yield of observed ions due to different isotopic composition of chlorinated methanes.

First-principles approach to rotational-vibrational frequencies and infrared intensity forH2adsorbed in nanoporous materials

The absorption sites and the low-lying rotational and vibrational (RV) energy states for ${\mathrm{H}}_{2}$ adsorbed within a metal-organic framework are calculated via van der Waals density-functional theory. The induced dipole due to bond stretching is found to be accurately given by a first-principles-driven approximation using maximally localized Wannier function analysis. The strengths and positions of lines in the complex spectra of RV transitions are in reasonable agreement with experiment, and in particular explain the experimentally mysteriously missing primary line for parahydrogen.

On the bound-state solutions of the Manning–Rosen potential including an improved approximation to the orbital centrifugal term

The approximate analytical bound-state solution of the Schrödinger equation for the Manning–Rosen (MR) potential is found by taking a new approximation scheme to the orbital centrifugal term. The Nikiforov–Uvarov method is used in the calculations. We obtain analytic forms for the energy eigenvalues and the corresponding normalized wave functions in terms of Jacobi polynomials or hypergeometric functions for different screening parameters 1/b. The rotational–vibrational energy states for a few diatomic molecules are calculated for arbitrary quantum numbers n and l with different values of the potential parameter α. The present numerical results agree within five decimal digits with the previously reported results for different 1/b values. A few special cases of the s-wave (l=0) MR potential and the Hulthén potential are also studied.

ChemInform Abstract: Microwave Spectrum and ab initio Calculations of Indazole.

Abstract The microwave spectrum of indazole and its ND isotopomer has been investigated at 70°C. The tautomer with the NH group closer to the phenyl ring is found to be the more stable both by the analysis of the rotational spectrum and ab initio calculations. The second tautomer is calculated at HF/4–21G level of theory to be 2800 cm−1 higher in energy. Information on the dipole moment and the low energy vibrational excited states has also been obtained.

Analysis of femtosecond stimulated Raman spectroscopy of excited-state evolution in bacteriorhodopsin

The dispersive lines observed in time-resolved femtosecond stimulated Raman spectroscopy (FSRS), using a pair of 809 nm, 3 ps Raman pump, and 840-960 nm ultrashort probe pulse, for the first 500 fs photoisomerization dynamics in the excited state of bacteriorhodopsin, BR* (S(1)), created by a prior 500 nm, 35 fs actinic pump pulse, have previously been attributed to Raman initiated by nonlinear emission (RINE). We used four-wave mixing energy level diagrams to describe the FSRS process, which include RINE as a subset, and a 29-mode harmonic oscillator model for BR(568) in the calculations. Our calculations showed that FSRS of BR* effectively occurs from the ground vibrational state of each of the observed 800-1800 cm(-1) modes of S(1). The lifetime on S(1) determines the linewidth and decay of the dispersive lines, and is estimated to be approximately 600 fs, comparable to the stimulated emission decay time. The FSRS dipole couplings are from the ground vibrational state of S(1) to high energy vibrational states on BR (S(0)), and we place a fast decay lifetime of approximately 100 fs on S(0) which can be attributed to the correlation function from the many unobserved low frequency modes. The FSRS dispersive lines are shown to be due to the inverse Raman scattering term with mid |0><1| vibrational coherence on the S(1) surface, and are not due to RINE with vibrational coherence on the S(0) surface. Our calculations show that the RINE process gives rise to broad featureless spectra.

Radio frequency magnetic field effects on molecular dynamics and iron uptake in cage proteins

The protein ferritin has a natural ferrihydrite nanoparticle that is superparamagnetic at room temperature. For native horse spleen ferritin, we measure the low field magnetic susceptibility of the nanoparticle as 2.2 x 10(-6) m(3) kg(-1) and its Néel relaxation time at about 10(-10) s. Superparamagnetic nanoparticles increase their internal energy when exposed to radio frequency magnetic fields due to the lag between magnetization and applied field. The energy is dissipated to the surrounding peptidic cage, altering the molecular dynamics and functioning of the protein. This leads to an increased population of low energy vibrational states under a magnetic field of 30 microT at 1 MHz, as measured via Raman spectroscopy. After 2 h of exposure, the proteins have a reduced iron intake rate of about 20%. Our results open a new path for the study of non-thermal bioeffects of radio frequency magnetic fields at the molecular scale.

The electronic spectrum of the fluoroborane free radical. II. Analysis of laser-induced fluorescence and single vibronic level emission spectra

Subsequent to our spectroscopic detection of the HBX (X=F, Cl, Br) free radicals (S.-G. He, F. X. Sunahori, and D. J. Clouthier, J. Am. Chem. Soc. 127, 10814 (2005)), the electronic spectrum of the A (2)A(")Pi-X (2)A(') system of the fluoroborane (HBF) radical in the 600-745 nm region has been studied in detail using the pulsed discharge jet technique. The band system involves a linear-bent transition between the two Renner-Teller components of what would be a (2)Pi state at linearity. Using the results of our theoretical study of the ground and excited state vibrational energy levels and (11)B-(10)B isotope shifts (see the companion paper), the vibrational quantum numbers of the bands in the laser-induced fluorescence (LIF) spectra have been assigned. Rotational and vibrational analyses of the LIF and wavelength resolved emission spectra have been carried out, from which the linear excited state and the bent ground state equilibrium configurations have been confirmed. The ground state molecular geometry of HBF has been determined as r(0)(BH)=1.214(2) A, r(0)(BF)=1.303 4(5) A, and theta=120.7(1) degrees. Based on high-level ab initio calculations and symmetry considerations, predissociation of the excited state into H((2)S)+BF((1)Sigma(+)) on the ground state potential energy surface is identified as the cause of the breaking off of fluorescence in the LIF spectra.

Electronic Spectroscopy of an Isolated Halocarbocation: The Iodomethyl Cation CH2I+ and Its Deuterated Isotopomers

Building upon our recent observation of the gas-phase electronic spectrum of the iodomethyl cation (CH2I+), we report an extensive study of the electronic spectroscopy of CH2I+ and its deuterated isotopomers CHDI+ and CD2I+ using a combination of fluorescence excitation and single vibronic level (SVL) emission spectroscopies. The spectra were measured in the gas phase under jet-cooled conditions using a pulsed discharge source. Fluorescence excitation spectra reveal a dominant progression in nu3 (C-I stretch), the frequency of which is markedly smaller in the upper state. Rotational analysis shows that, while the A constant is similar in the two states, the excited state has significantly smaller B and C constants. These results indicate a lengthening of the C-I bond upon electronic excitation, consistent with calculations which show that this transition is analogous to the well-known pi-pi* transition in the isoelectronic substituted formaldehydes. SVL emission spectra show progressions involving four of the six vibrational modes; only the C-H(D) stretching modes remain unobserved. The vibrational parameters determined from a Dunham expansion fit of the ground state vibrational term energies are in excellent agreement with the predictions of density functional theory (DFT) calculations. A normal-mode analysis was completed to derive a harmonic force field for the ground state, where resonance delocalization of the positive charge leads to partial double bond character, H2C+-I <--> H2C=I+, giving rise to a C-I stretching frequency significantly larger than that of the iodomethyl radical.

Energy transfer of highly vibrationally excited naphthalene. I. Translational collision energy dependence

Energy transfer between highly vibrationally excited naphthalene and Kr atom in a series of translational collision energies (108-847 cm(-1)) was studied separately using a crossed-beam apparatus along with time-sliced velocity map ion imaging techniques. Highly vibrationally excited naphthalene in the triplet state (vibrational energy: 16,194 cm(-1); electronic energy: 21,400 cm(-1)) was formed via the rapid intersystem crossing of naphthalene initially excited to the S(2) state by 266 nm photons. The collisional energy transfer probability density functions were measured directly from the scattering results of highly vibrationally excited naphthalene. At low collision energies a short-lived naphthalene-Kr complex was observed, resulting in small amounts of translational to vibrational-rotational (T-->VR) energy transfer. The complex formation probability decreases as the collision energy increases. T-->VR energy transfer was found to be quite efficient at all collision energies. In some instances, nearly all of the translational energy is transferred to vibrational-rotational energy. On the other hand, only a small fraction of vibrational energy is converted to translational energy. The translational energy gained from vibrational energy extend to large energy transfer (up to 3000 cm(-1)) as the collision energy increases to 847 cm(-1). Substantial amounts of large V-->T energy transfer were observed in the forward and backward directions at large collision energies.

Electronic spectroscopy of jet-cooled HCP+: Molecular structure, phosphorus hyperfine structure, and Renner-Teller analysis

Laser-induced fluorescence spectra of jet-cooled HCP(+) and DCP(+) have been obtained with the pulsed discharge technique using HCPDCP and argon precursor mixtures. Transitions involving all of the excited state vibrations have been observed and a set of vibrational constants has been obtained. High-resolution spectra of the (2)Pi(32) components of the 0(0) (0) bands of both isotopomers have been recorded, and these spectra show resolved phosphorus hyperfine structure which allowed the determination of the excited state Fermi contact parameter. The B values were used to obtain the ground and excited state effective geometric parameters as r(0) (")(CH)=1.077(2) A, r(0) (")(CP)=1.6013(3) A, r(0) (')(CH)=1.082(2) A, and r(0) (')(CP)=1.5331(3) A. A Renner-Teller analysis of the ground state vibrational energy levels obtained from the literature was attempted. All of the observed levels of DCP(+) and the majority of those of HCP(+) were satisfactorily fitted with a standard Renner-Teller model, but three HCP(+) levels showed large systematic deviations which could not be accommodated by reassignments or improvements in the Fermi resonance Hamiltonian. Further improvements in the theory or in the experimental data will be needed to resolve this discrepancy.

Dependence of particle fluctuation velocity on gas flow, and particle diameter in gas fluidized beds for monodispersed spheres in the Geldart B and A fluidization regimes

In this paper we present new experimental data on the steady-state, mean squared, fluctuation velocity, or granular temperature, of Geldart B polymer, glass, nickel, and stainless steel monodispersed spheres averaged over the wall of a gas fluidized bed, as a function of gas flow and sphere diameter. The granular temperature is obtained by Acoustic Shot Noise technology—namely power spectral analysis of the steady state vibrational energy of the wall excited by random sphere impact, and calibrated by hammer excitation over the wall. The new data extends to polymer and metallic spheres the experimental discovery of a 1996 paper of Cody et al. that the fluctuation velocity of Geldart B glass spheres when scaled to the gas superficial velocity, U s, is inversely proportional to sphere diameter, directly proportional to a fundamental length scale, D o B, and is a universal function of U = ( U s / U mf). We also demonstrate that the new data is consistent with the diameter dependence of the fluctuation velocity that can be derived from both the 1997 paper of Menon and Durian, who measured random sphere motion near the wall through the spectroscopy of scattered laser light, and the 1992 paper of Rahman and Campbell, who measured the average granular pressure of random sphere impact on a porous steel membrane. While the inverse scaling of the fluctuation velocity with sphere diameter, and the existence of a fundamental length scale for gas fluidization, D o B, had not been a feature of any published fundamental model, or computer simulation, of the steady state granular temperature of spheres in gas fluidized beds, we show that it is a feature of two recent dense kinetic fluidization models published in 1999, by Buyevich and Kapbasov, and Koch and Sangani. Both theories implicitly define a fundamental length scale for the fluctuation velocity, D ⁎ = ( μ f 2 / ρ p 2 g) 1 / 3 , where ρ p is the sphere density, μ f is the gas viscosity, and g is the laboratory gravitational field. The new data for polymer, glass, nickel and stainless steel spheres presented in this paper, defines D o B = (56 ± 2) D ⁎. We use the Anderson–Jackson stability model to show that the length scale D o B, also defines a stability length scale, such that for D < D o B( D > D o B), the uniform dense phase of the fluidized bed is stable (unstable), against one dimensional, first order fluctuations in sphere concentration. The length scale, D o B is thus the theoretical equivalent to the empirical scaling length introduced by Geldart, D B/A, to distinguish spheres ( D > D B/A) that bubble at fluidization, from spheres ( D < D B/A) that fluidize before bubbling. Finally, we present new experimental data, on the remarkable changes in the granular temperature, bed expansion, and bed collapse time, between Geldart B and Geldart A monodispersed glass spheres, and compare that data to granular temperature, and bed expansion, for Geldart A rough, non-spherical, log-normal dispersed diameter catalytic particles.