Vibrational Energy Research Articles

Enantioselectivity from inelastic electron tunnelling through a chiral sensor

The vibration theory of olfaction, which explains it as the sensing of odorant molecules by their vibrational energies through inelastic electron tunnelling spectroscopy (IETS) has inspired olfactory sensor ideas. However, this theory has been presumed inadequate to explain the difference in smell between enantiomers (chiral molecules, which are mirror images of each other), since these have identical vibrational spectra. Going beyond phenomenological assumptions of enantioselective tunnelling, we show on the basis of ab initio modelling of real chiral molecules, that this drawback is indeed obviated for IETS-based olfactory sensors if they are chiral. Our treatment unifies IETS with chirality induced spin selectivity, which explains that charge polarization in chiral molecules by accompanied by spin polarization. First, we apply ab initio symmetry adapted perturbation theory to explain and illustrate enantioselective coupling of chiral odorant molecules and chiral olfactory sensors. This naturally leads to enantioselective coupling of the vibrational mode of an odorant to electron transport (electron-vibron coupling) in an IETS-based sensor when both odorant and sensor are chiral. Finally, we show, from phenomenological quantum transport calculations, that that in turn results in enantioselective IET spectra. Thus, we have demonstrated the feasibility of enantioselective sensing within a vibration framework. Our work also limns the possibility of quantum biomimetic electronic nose sensors that are enantioselective, a feature which could open up new sensing applications.

Electronic structure, spectroscopy and photophysics of rubidium mono-sulphide

We investigated the nineteen first electronic states of the RbS diatomic using post Hartree-Fock configuration interaction methods at the internally contracted multi-reference configuration interaction (MRCI+(Q)) level. We thus mapped their respective potential energy curves with and without considering spin-orbit effects. After nuclear motion treatments, we derived their equilibrium distances, rotational and vibrational constants, and dissociation and electronic excitation energies. Moreover, an evaluation of the dipole moments of RbS was conducted, which in turn were used to evaluate the radiative lifetimes of the vibrational levels of RbS (X2П and A2Σ+) states. Computations show that spin-orbit interactions are important and cannot be omitted. Afterwards, and utilizing the sum rule approximation and the Franck–Condon factors, we computed both the bound-bound contributions and the bound-free terms. Our findings suggest that RbS exhibits intriguing characteristics suitable for laser cooling experiments. In sum, this work contributes to the understanding in-depth of the spectroscopy of RbS and predicts its use as a promising molecular system for laser cooling applications.

Physical adsorption of the Ba atom on Arn surfaces: spectroscopic and geometric properties

Barium atoms cause several environmental and ecological dangers. Numerous techniques are employed to remove the Ba atom such as physisorption and solvation methods. In this work, we are interested in investigating and exploring the Ba atom’s physical adsorption on argon surfaces. We have tested several optimizations and we have found that the first range of Ar atoms (n = 1–12) presents more than 90% of the energy interaction between Ba and the adsorbent surface. Therefore, we started by computing and analyzing the potential energy surfaces (PESs) of BaArn molecules. Large basis sets and full Configurations Interaction (full-CI) with the pseudo-potential approach were used to perform the PES, the spectroscopic parameters, vibrational energy levels, and electric dipole moment (EDM) for the selected states. The structural properties and relative stability of Ba (6s2 1S)Arn (n = 1–13, 30, 44, and 54) clusters are determined using Monte Carlo simulation based on the Potential Model method (MC-PM). Several clusters (n > 4) were demonstrated to be stable using MC simulations, and the Ba atom is always present on the surface of the remaining Arn cluster. We have found a good concordance between our results and the available theoretical and experimental data. The spectroscopic information of these complexes can be used by experimental researchers for the investigation of optical mechanisms collision, especially the deformation of the Ba spectrum by collision with the argon surface.

Ab initio spectroscopic studies of AlF and AlCl molecules

In this work, we report the results from our spectroscopic study on AlF and AlCl molecules. We carry out detailed electronic structure calculations in both the molecules, including obtaining the potential energy surfaces of the [Formula: see text] ground electronic state and some of the low-lying excited electronic states belonging to [Formula: see text] and [Formula: see text] symmetries. This is followed by evaluating the spectroscopic constants and molecular properties such as electric dipole moments and electric quadrupole moments. Throughout, we employ the multi-reference configuration interaction method and work with high-quality quadruple zeta basis sets. Further, transition dipole moments between the ground electronic state and singlet excited states are also studied. The relevant vibrational parameters are computed by solving the vibrational Schrödinger equation. Subsequently, the vibrational energy spacings and transition dipole moments between the vibrational levels belonging to the same electronic states are used to evaluate the spontaneous and black-body radiation-induced transition rates, followed by computing the lifetimes. Finally, the energy differences between rotational levels belonging to different vibrational levels and within an electronic state as well as the Einstein coefficients are reported.

Infrared Laser Stark Spectroscopy of Methyl Fluoride in 4He Nanodroplets.

We measured the rotationally resolved infrared spectra of helium solvated methyl fluoride at 3 μm and 10 μm, wherein lies C-H and C-F stretching bands, respectively. The linewidths (FWHM) were found to increase with increasing vibrational energy and range from 0.002 cm-1 in the v3 band (C-F stretch) at ~1047 cm-1, to 0.65 cm-1 in the v4 band (asymmetric C-H stretch) at ~2997 cm-1. In between these two bands we observed the lower and upper components of the Fermi triad bands (ν1/2ν2/2ν5) at ~2859 and ~2961 cm-1. We carried out Stark spectroscopy on the lower band on account of its narrower linewidths (0.04 vs. 0.14 cm-1, respectively). The objective of performing Stark spectroscopy was to see if there is any evidence for a rotational linewidth dependence on the external field strength, due to a reduced difference in between methyl fluorides rotational energy gap and the roton-gap of superfluid helium. We did not find any evidence for such an effect, which we largely attribute to the rotational energy gap not increasing significantly enough by the external field. We point to another molecule (formaldehyde) whose energy levels are predicted to show a more promising response to application of an external field.

Tell Machine Learning Potentials What They Are Needed For: Simulation-Oriented Training Exemplified for Glycine.

Machine learning potentials (MLPs) are widely applied as an efficient alternative way to represent potential energy surfaces (PESs) in many chemical simulations. The MLPs are often evaluated with the root-mean-square errors on the test set drawn from the same distribution as the training data. Here, we systematically investigate the relationship between such test errors and the simulation accuracy with MLPs on an example of a full-dimensional, global PES for the glycine amino acid. Our results show that the errors in the test set do not unambiguously reflect the MLP performance in different simulation tasks, such as relative conformer energies, barriers, vibrational levels, and zero-point vibrational energies. We also offer an easily accessible solution for improving the MLP quality in a simulation-oriented manner, yielding the most precise relative conformer energies and barriers. This solution also passed the stringent test by diffusion Monte Carlo simulations.

Extended improved multiparameter exponential‐type potential energy function for diatomic molecules

AbstractBased on the improved multiparameter exponential‐type potential (IMPET), an extended IMPET (EIMPET) potential has been suggested to reduce the discrepancy between the calculated and experimental values, improving the accuracy near the equilibrium and in the asymptotic region. The average fitting deviation δav and Root‐Mean‐Square (RMS) error is used to evaluate the performance of the potential which generates potential energy curves (PECs) and vibrational energy levels for ClF‐A(3Π1), CP‐X2Σ+, ICl‐X1Σ+, IBr‐X1Σ+, CO‐X1Σ+, and 6Li2‐X1Σ+ molecules that agree better with the Rydberg‐Klein‐Rees (RKR) data than Morse, Huxley‐Murrell (HM) and IMPET potentials. This work provides a reference for the construction and improvement of potential energy functions for diatomic molecules.

ЗВУКОВАЯ ТЕРАПИЯ И МУЗЫКАЛЬНАЯ МЕДИЦИНА: БИОЛОГИЧЕСКИЕ МЕХАНИЗМЫ (Часть 2)

This article provides clinicians and other medical professionals with an introduction to the related fields of Sound Therapy and Music Medicine, outlining some of the many biological mechanisms advantageously activated by these modern modalities. The umbrella term for audible sound therapies is often popularly referred to as «Vibrational Medicine», embracing the energetic (vibrational) interconnectedness of the mind-body system. The information provided is intended for physicians, psychologists, music therapists, nurses, integrative medicine practitioners, and wellness practitioners utilizing the therapeutic potential of Vibrational Medicine. Since the body is comprised of vibrational energy, a wide variety of energetic modalities are available to support the patient’s physiology, and the article describes some of the many physiological mechanisms initiated by Sound Therapy and Music Medicine, perhaps most importantly, pain mediation, achieved by locally applied specific sound frequencies. Other mechanisms, such as vagal stimulation, are described and achieved by experiencing specific sound frequencies or music via headphones. The article is in two parts: Part 1 was published in the past issue (3-2023) of the «Medicine and Art» journal (https://doi.org/10.60042/2949-2165-2023-1-3-60-93). It provides a short history of therapeutic sound, followed by definitions of Music Therapy, Music Medicine, and Sound Therapy, followed by sections on some of the many biological mechanisms activated by full body immersion in music or specific sound frequencies, including an introduction to pain mediation by sound. Part 2 includes breaking the pain-spasm pain cycle in spinal injury by sound; pain relief and anxiety relief by acupressure and sonopuncture; oxygen-driven healing by sound; musical stimulation of the immune system; sonic stimulation of the vagus nerve via headphones and by vocalizations; and last, a look into the future of vibrational medicine.

Characteristics of Far-Infrared Ray Emitted from Functional Loess Bio-Balls and Its Effect on Improving Blood Flow.

XRD diffraction and IR absorption were investigated for raw loess powder and heat-treated loess powder. Raw loess retains its useful minerals, but loses their beneficial properties when calcined at 850 °C and 1050 °C. To utilize the useful minerals, loess balls were made using a low-temperature wet-drying method. The radiant energy and transmittance were measured for the loess balls. Far-infrared ray (FIR) emitted from loess bio-balls is selectively absorbed as higher vibrational energy by water molecules. FIR can raise the body's core temperature, thereby improving blood flow through the body's thermoregulatory mechanism. In an exploratory study with 40 participants, when the set temperature of the loess ball mat was increased from 25 °C to 50 °C, blood flow increased by 39.01%, from 37.48 mL/min to 52.11 mL/min, in the left middle finger; in addition, it increased by 39.62%, from 37.15 mL/min to 51.87 mL/min, in the right middle finger. The FIR emitted from loess balls can be widely applied, in various forms, to diseases related to blood flow, such as cold hands and feet, diabetic foot, muscle pain, and menstrual pain.

Dynamical Tunneling in More than Two Degrees of Freedom.

Recent progress towards understanding the mechanism of dynamical tunneling in Hamiltonian systems with three or more degrees of freedom (DoF) is reviewed. In contrast to systems with two degrees of freedom, the three or more degrees of freedom case presents several challenges. Specifically, in higher-dimensional phase spaces, multiple mechanisms for classical transport have significant implications for the evolution of initial quantum states. In this review, the importance of features on the Arnold web, a signature of systems with three or more DoF, to the mechanism of resonance-assisted tunneling is illustrated using select examples. These examples represent relevant models for phenomena such as intramolecular vibrational energy redistribution in isolated molecules and the dynamics of Bose-Einstein condensates trapped in optical lattices.

No Headache for PIPs: A PIP Potential for Aspirin Runs Much Faster and with Similar Precision Than Other Machine-Learned Potentials.

Assessments of machine-learning (ML) potentials are an important aspect of the rapid development of this field. We recently reported an assessment of the linear-regression permutationally invariant polynomial (PIP) method for ethanol, using the widely used (revised) rMD17 data set. We demonstrated that the PIP approach outperformed numerous other methods, e.g., ANI, PhysNet, sGDML, and p-KRR, with respect to precision and notably with respect to speed [Houston et al., J. Chem. Phys. 2022, 156, 044120]. Here, we extend this assessment to the 21-atom aspirin molecule, using the rMD17 data set, with a focus on the speed of evaluation. Both energies and forces are used for training, and the precision of several PIPs is examined for both. Normal mode frequencies, the methyl torsional potential, and 1d vibrational energies for an OH stretch are presented. We show that the PIP approach achieves the level of precision obtained from other ML methods, e.g., atom-centered neural network methods, linear regression ACE, and kernel methods, as reported by Kovács et al. in J. Chem. Theory Comput. 2021, 17, 7696-7711. More significantly, we show that the PIP PESs run much faster than all other ML methods, whose timings were evaluated in that paper. We also show that the PIP PES extrapolates well enough to describe several internal motions of aspirin, including an OH stretch.

High Performance and Stackable Trampoline Like‐Triboelectric Vibration Energy Harvester for In‐Situ Powering Sensor Node with Data Wirelessly Transmitted Over 1000‐m

AbstractAddressing the power supply challenges of wireless sensor nodes is pivotal for advancing the development of the Internet of Things (IoT). This work proposes a high performance and stackable trampoline like‐triboelectric vibration energy harvester (T‐TVEH) that can efficiently harvest ultra‐wideband vibrational energy for in‐situ powering of sensor nodes. The unique structural design and material selection enables T‐TVEH to represent a breakthrough in terms of both working bandwidth and power density compared to recent research efforts of vibration energy harvesting. Specifically, the working bandwidth and the peak power density of T‐TVEH is 192 Hz and 5.9 W m−2, which are higher than previous related studies by 156% and 59.2%, respectively. Based on the excellent performance of the T‐TVEH, a wireless sensor node for monitoring machinery condition is constructed. Temperature, humidity, and frequency information are successfully acquired and transmitted to 1000‐m through the wireless sensor node, which is nine times improved compared to related studies. Meanwhile, it achieves fully self‐powered wireless operation monitoring and abnormal alarm on a real ship's marine diesel engine. Overall, this study proposed an innovative solution for in‐situ power supply of wireless sensor nodes, which has broad application prospects in the field of the IOT.

The FTIR spectra of Ag/Ag2O composites doped with silver nanoparticles

In this work, we studied the effect of silver nanoparticles on the IR absorption mechanism in Ag/Ag2O composites. Ag/Ag2O composites were prepared by exposing silver films prepared by thermal evaporation to oxygen plasma afterglow. The infrared spectra of these samples were analysed. The results obtained showed that, the individual silver nanoparticles affect the vibrations of chemical bonds in Ag/Ag2O composites, and this is inferred from the gradual decrease in intensity when moving towards lower wavenumbers. In addition, it was found that the effect of individual silver nanoparticles is greatest in the frequency range of Ag–O bond vibrations and becomes weaker in the case of bonds with higher vibration energies.

Unraveling the Ultrafast Photochemical Dynamics of Nitrobenzene in Aqueous Solution.

Nitroaromatic compounds are major constituents of the brown carbon aerosol particles in the troposphere that absorb near-ultraviolet (UV) and visible solar radiation and have a profound effect on the Earth's climate. The primary sources of brown carbon include biomass burning, forest fires, and residential burning of biofuels, and an important secondary source is photochemistry in aqueous cloud and fog droplets. Nitrobenzene is the smallest nitroaromatic molecule and a model for the photochemical behavior of larger nitroaromatic compounds. Despite the obvious importance of its droplet photochemistry to the atmospheric environment, there have not been any detailed studies of the ultrafast photochemical dynamics of nitrobenzene in aqueous solution. Here, we combine femtosecond transient absorption spectroscopy, time-resolved infrared spectroscopy, and quantum chemistry calculations to investigate the primary steps following the near-UV (λ ≥ 340 nm) photoexcitation of aqueous nitrobenzene. To understand the role of the surrounding water molecules in the photochemical dynamics of nitrobenzene, we compare the results of these investigations with analogous measurements in solutions of methanol, acetonitrile, and cyclohexane. We find that vibrational energy transfer to the aqueous environment quenches internal excitation, and therefore, unlike the gas phase, we do not observe any evidence for formation of photoproducts on timescales up to 500 ns. We also find that hydrogen bonding between nitrobenzene and surrounding water molecules slows the S1/S0 internal conversion process.

Relativistic coupled cluster study on the spectroscopic and radiative properties of the KFr molecule and modeling of the transport properties of potassium–francium dilute gas medium

The KFr diatomic molecule represents a promising candidate for photoassociation and indirect laser cooling. It has not yet been investigated experimentally and remains the only representative of the family of alkali-metal diatomics, which is scarcely researched theoretically. The potential energy curves of the states belonging to the three lowest dissociation limits of the KFr molecule are calculated using the Fock-space relativistic coupled cluster theory for the first time. Properties and parameters, such as electronic term energies, equilibrium internuclear distances, transition and permanent dipole moments, sequences of vibrational energies, harmonic vibrational frequencies, Franck–Condon factors, and radiative lifetimes (including bound and free transitions), are predicted. We analyzed and evaluated the probabilities of the two-step schemes (optical cycles) for the transfer process of the KFr molecules from excited vibronic states to the ground vibronic state. The transport properties (diffusion, viscosity, and thermal conductivity coefficients) of two-component dilute gas media of potassium and francium atoms as functions of the translation temperature up to 3000 K are also calculated. The data obtained would be useful for laser cooling and spectral experiments with KFr molecules.

Studying substituent number effects on vibrational energy transfer by time−resolved CARS spectroscopy

Studying substituent number effects on vibrational energy transfer by time−resolved CARS spectroscopy

Vibrational energy harvesting and tactile sensing applications based on PVDF-TPU piezoelectric nanofibers

Vibrational energy harvesting and tactile sensing applications based on PVDF-TPU piezoelectric nanofibers

Line shapes of isotropic and depolarized CILS spectra of neon: Interaction potential and pair polarizability

The present work proposes three interaction potentials between two gaseous neon atoms and applies them to the study of models representing the anisotropy and trace of the induced pair polarizability tensor. The proposed empirical interatomic potentials for the gaseous Ne-Ne interaction are developed by fitting the Improved Lennard-Jones (ILJ), Modified Tang-Toennies (MTT) and Barker et al. (BFW) potentials simultaneously to the spectroscopic and transport properties over a wide temperature range. The validity of the proposed interatomic potentials is verified by comparing the calculated and experimental second pressure virial coefficient over a wide temperature range. In addition to this, the results show satisfactory accordance between the experimental and calculated vibrational energy levels using the deduced pair potential parameters compared to those reported for neon gas. These comparisons exhibit acceptable accuracy when the present work potential parameters are inserted to reproduce the transport and thermo-physical properties, besides the spectral moments and the spectral line-shape intensities for neon gas. The isotropic and depolarized collision-induced light scattering (CILS) spectra are produced and analyzed as functions of the potential considered. They exhibit sensitivity to both the attractive part of the potential and the short-range values of the polarizability anisotropy or mean at intermediate and high frequencies. Mean and anisotropy are deduced directly from spectral line shapes using a new inversion method.

Evaluation of the Baha SoundArc in children

ObjectiveThe Baha SoundArc coupling system has been developed as a non-surgical coupling of a Baha sound processor to the skull allowing the transfer of vibrational energy to the cochlear partition via bone conduction pathways. Today, there are several alternatives to this non-surgical approach as the Baha headband/test band, or the Baha Softband, or adhesive patches. Each of these current options have benefits and liabilities. The aim of the study was to evaluate pediatric experience and performance when using two non-surgical options, the Baha SoundArc compared to the Baha Softband. MethodsTwenty-five children with unilateral mixed or conductive hearing loss aged 5–12 years of age evaluated the use of the Baha SoundArc compared to their existing Baha Softband in a one month take home trial. Participants had a minimum of 3 months experience using the control, Baha Softband. Participants were assessed at baseline and one month following fit of the Baha SoundArc. Measures included an experience and use patient reported outcome, speech perception testing in quiet using Phonetically Balanced Kindergarten (PBK) words, and sound field audiometry. ResultsMean aided soundfield thresholds across the frequency range were 27.6 dB HL for Softband and 26.0 dB HL for SoundArc, which were not significantly different (P = >.05). Mean word recognition score was 80.8% when aided with the Softband device and 85.1% with the SoundArc, which was also not significantly different (P = >.05). Most children favored the aesthetics and usability of the SoundArc over Softband, but comfort ratings were largely similar for both devices. ConclusionsBone conduction sound processors mounted on a SoundArc or a Softband resulted in comparable improvements in aided thresholds and speech understanding in children suffering from conductive or mixed hearing loss. Both wearing modalities can be considered equivalent in terms of audiological outcomes, although both patients and clinicians preferred the usability and aesthetics of the SoundArc. The SoundArc provides an alternative wearing option for patients that may otherwise be discouraged by the aesthetics and usability of the Softband device. Clinicaltrials.gov identifierNCT03333577.

Molecular Dynamics Simulation of Thermal Nonequilibrium and Chemical Reaction Processes in Hydrogen Combustion.

Using reactive force field (ReaxFF) and molecular dynamics simulation, we investigate the combustion process of hydrogen-oxygen systems in initial thermal nonequilibrium states with different translational and rovibrational temperatures for oxygen. The system studied in this work contains 300 oxygen molecules and 700 hydrogen molecules with a density of 7 times the air density. For this system, the characteristic relaxation times of oxygen and hydrogen vibrational energies are 0.173 and 0.249 ns, respectively. 0.6% of hydrogen undergoes a chemical reaction with oxygen during the thermal nonequilibrium relaxation stage. For the distribution of translational energy and vibrational energy of oxygen in the thermal nonequilibrium state, the maximum mean error of the statistical distribution in the simulation and the Boltzmann distribution at temperature calculated from the average kinetic energy of molecules is about 2.25 × 10-5. At the same time, it was observed in the simulation that many-body interactions play a certain role in the combustion process. Furthermore, we compare the ignition time and temperature rise behavior of different combustion mechanisms and molecular dynamics simulations starting from the thermal equilibrium state. These results will provide meaningful references for the construction of thermal nonequilibrium combustion chemical reaction mechanisms.