Vibrational States Research Articles

Source and mask optimization for stability of reticle and wafer stages

The relative motion of the reticle stage and wafer stage caused by vibration during the scanning exposure process of the lithography machine is an important factor that affects the imaging quality under limited lithography ability. In this paper, the influence of the vibration of the lithography stage system on the lithography imaging quality is studied. The lithography model including the vibration error of the stage is taken into account in the framework of source and mask optimization (SMO). For the 193-nm immersion lithography machine, combined with different design patterns with a line width of 40 nm and different vibration states of the stage when the lithography machine is exposed, the SMO joint optimization research is carried out, and the robustness of the stage under the limit process after SMO optimization is explored. The research results show that the contrast and relative light intensity change of the limit design figure under the influence of moving standard deviation (MSD) will greatly affect the linewidth at the light intensity threshold and then affect the process window (PW). The SMO including MSD allows the MSD to change in the range of 0-6 nm without changing the PW.

Gearbox fault diagnosis based on RGT-MFFIN and multi-sensor fusion image generation

Abstract In gearbox fault diagnosis based on vibration and torque state data, traditional one-dimensional time-frequency domain analysis methods often suffer from insufficient feature expression and mining, and require complex noise reduction and filtering preprocessing. To address this issue, this paper proposes a fusion image generation method that integrates the advantages of recurrence plot (RP) and Gramian angular summation field (GASF) to generate recurrence Gramian transformed (RGT) images. This approach integrates both global and local fault information, making the fault characteristics more intuitive and easier to analyze. Given that multi-sensor collaboration can enhance feature representation, feature-level fusion increases the computational burden, and decision-level fusion is prone to losing inter-sensor correlation information, this paper adopts data-level fusion for image sample enhancement. In the diagnostic method, the challenge of traditional convolutional neural networks (CNNs) in extracting diverse geometric linear structures from fused images is addressed by introducing deformable convolutional blocks for initial feature extraction. Additionally, a multi-scale feature fusion interaction network (MFFIN) is constructed. This network incorporates a channel-space interactive attention mechanism on top of multi-scale feature extraction, assigning weights to features according to their importance while facilitating the interaction of feature information. Finally, validation is carried out using public datasets, and the experimental results show that the proposed method demonstrates significant advantages in classification accuracy and robustness under variable operating conditions and noise, thereby proving its effectiveness and practicality.

MRCI+Q calculations on electronic structure and spectroscopy of low-lying electronic states of silicon monobromide including spin-orbit coupling effect

The electronic structures of silicon monobromide (SiBr) correlating with the lowest three dissociation channels are studied using high-level configuration interaction method. The spin-orbit coupling (SOC) effect and core-valence (CV) correlations effect are taken into account to improve the accuracy of electronic structures. Based on the calculated electronic structures of the lowest three dissociation channels of SiBr, the spectroscopic constants of quasibound and bound electronic states are fitted, which are coincided with the results of experiment. The dipole moment curves (DMs) of the lowest three dissociation channels of SiBr are obtained, and the abrupt change of DMs nearby the avoided crossing point are explained by the variation of electronic configurations of the corresponding states. With the help of the calculated SOC matrix elements, the predissociation channels of the low-lying vibrational states of 2Δ(Ⅱ) and 2Π(Ⅲ) sates are analyzed. The complicated interaction between crossing states is investigated. The ν'≥0 vibrational states of 2Δ(Ⅱ) and ν′≥2 vibrational states of 2Π(Ⅲ) would predissociate rapidly through predissociation channels of 2Δ(Ⅱ)-2Π(Ⅱ) and 2Π(Ⅲ)-2Σ+(Ⅱ). Finally, the transition properties of A2Σ+-X2Π, 2∆(Ⅱ)-X2Π, 2Σ+(Ⅱ)-X2Π, 2Π(Ⅲ)-X2Π, 1/2(Ⅱ)-X2Π1/2, 1/2(Ⅲ)-X2Π1/2 and 3/2(Ⅱ)-X2Π1/2 transitions are investigated, and radiative lifetime of bound states are evaluated.

Evaluation of highly sensitive vibration states of nanomechanical resonators in liquid using a convolutional neural network

Nanomechanical resonators can detect various small physical quantities with high sensitivity using changes in resonant properties. However, viscous damping in liquids significantly reduces the measurement sensitivity. This study proposes convolutional neural network (CNN) vibration spectrum analysis to evaluate the highly sensitive vibration states of nanomechanical resonators, which are useful for in-liquid measurements. This research was carried out through the measurement of acetone concentration. First, we compared the concentration classification ability between the proposed and conventional methods and determined that the proposed method of analyzing vibration spectral changes using the CNN model can provide higher measurement sensitivity than the conventional measurement method of observing resonance properties changes and comparing the values for each measurement condition. This result shows that CNN-based spectral analysis is effective for the vibration spectra of in-liquid measurements. Next, gradient-weighted class activation mapping (Grad-CAM) was applied to verify which frequency bands are important for concentration classification in CNN model decision-making. The vibration states in these frequency bands were analyzed in terms of oscillation modes. This analysis revealed significant oscillation modes of the nanomechanical resonator in the liquid environment. Notably, in addition to the resonance states utilized in the conventional method, several other oscillation modes were found to be significant for measurements. This finding suggests that these oscillation modes may be highly sensitive for measurements in liquid environments. Among these oscillation modes, the mode with very small amplitude is highly promising for achieving unprecedented levels of sensitivity in sensing technologies.

Variational Vibrational States of Methanol (12D).

Full-dimensional (12D) vibrational states of the methanol molecule (CH3OH) have been computed using the GENIUSH-Smolyak approach and the potential energy surface from Qu and Bowman (2013). All vibrational energies are converged better than 0.5 cm-1 with respect to the basis and grid size up to the first overtone of the CO stretch, ca. 2000 cm-1 beyond the zero-point vibrational energy. About 70 torsion-vibration states are reported and assigned. The computed vibrational energies agree with the available experimental data within less than a few cm-1 in most cases, which confirms the good accuracy of the potential energy surface. The computations are carried out using curvilinear normal coordinates with the option of path-following coefficients, which minimize the coupling of the small- and large-amplitude motions. It is important to ensure tight numerical fulfillment of the C3v(M) molecular symmetry for every geometry and coefficient set used to define the curvilinear normal coordinates along the torsional coordinate to obtain a faithful description of degeneracy in this floppy system. The reported values may provide a computational reference for fundamental spectroscopy, astrochemistry, and for the search of the proton-to-electron mass ratio variation using the methanol molecule.

Thermomagnetic Models for the Improved Rosen–Morse Oscillator

ABSTRACTThis study solves the radial Schrödinger wave equation (RSWE) with the improved Rosen–Morse (IRM) potential constrained by an electromagnetic field. Energy eigenvalues are derived using the parametric Nikiforov–Uvarov method and Pekeris approximation. The internal partition function, isobaric molar heat capacity formula, and magnetization model are then deduced from the equation governing pure vibrational energy states. These analytical models are applied to several pure substances, specifically Br2 (X 1Σg+), BrF (X 1Σ+), ICl (X 1Σg+), and P2 (X 1Σg+) molecules. Numerical approximations of the energy eigenvalues for these molecules closely match their exact values. The isobaric molar heat capacity expression yields mean percentage absolute deviations of 1.6585%, 0.9162%, 1.2193%, and 0.7232% when compared against experimental data for Br2 (X 1Σg+), BrF (X 1Σ+), ICl (X 1Σg+), and P2 (X 1Σg+), respectively. These results align well with other heat capacity models in existing literature.

Dynamics of the Cl + CH3CN reaction on an automatically-developed full-dimensional abinitio potential energy surface.

A full-dimensional analytical potential energy surface (PES) is developed for the Cl + CH3CN reaction following our previous work on the benchmark abinitio characterization of the stationary points. The spin-orbit-corrected PES is constructed using the Robosurfer program and a fifth-order permutationally invariant polynomial method for fitting the high-accuracy energy points determined by a ManyHF-based coupled-cluster/triple-zeta-quality composite method. Quasi-classical trajectory simulations are performed at six collision energies between 10 and 60kcal mol-1. Multiple low-probability product channels are found, including isomerization to isonitrile (CH3NC), but out of the eight possible channels, only the H-abstraction has significant reaction probability; thus, detailed dynamics studies are carried out only for this reaction. The cross sections and opacity functions show that the probability of the H-abstraction reaction increases with increasing collision energy (Ecoll). Scattering angle, initial attack angle, and product relative translational energy distributions indicate that the mechanism changes with the collision energy from indirect/rebound to direct stripping. The distribution of initial attack angles shows a clear preference for methyl group attack but with different angles at different Ecoll values. Post-reaction energy distributions show that the energy transfer is biased toward the products' relative translational energy instead of their internal energy. Rotational and vibrational energy have about the same amount of contribution to the internal energy in the case of both products (HCl and CH2CN), i.e., both of them are formed with high rotational excitations. HCl is produced mostly in the ground vibrational state, while a notable fraction of CH2CN is formed with vibrational excitation.

Synchrotron radiation far infrared spectrum of the astrophysically significant Ethanol (CH3CH2OH) molecule in the gauche states in the vibrational ground state and other infrared observations

In this communication, the analyses of synchrotron radiation far infrared (FIR) spectrum corresponding to the gauche- (e1ando1) states of Ethyl Alcohol are reported. Detailed assignments have been performed for b-type transitions for K values ranging from 5 to 32 and up to a maximum J value of 50. The assignments confirmed the earlier microwave (MW) and millimeter wave (MMW) spectroscopic results. The transition wavenumbers have been used to determine the term values for the gauche-states involved for all the K and J values for which observation has been made. About 2000 spectral lines have been assigned, including some accurately calculated lines that fall in the MW and MMW regions. Although transitions between the trans-species and gauche species are not allowed in Ethanol, many resonances and level crossings of energy levels cause forbidden transitions. One such system of level crossings between K=10o1 and 12ee00 has been analyzed in detail, and the interaction coefficient determined. The state mixing seems quite strong and causes forbidden transitions (ΔK=0,2,3), including transitions for trans↔gauche, have been found. In addition, many new strong transitions have been assigned, which belong to the trans-species. To extend our work to higher wave numbers to facilitate observations made by the infrared detector on board the James Webb Space Telescope (JWST), the analysis of the torsional fundamental band transitions (around 220cm-1) for o2←e0 and o2←e1 has been taken up. Some of the assignments are discussed here. Lastly, the lower-lying vibrational bands centered around 425cm-1 (CCO– bending mode) and the band at around 800cm-1 (CH3- rocking mode) have been recorded. The CCO bending band shows an unmistakable parallel character for the trans-species. The assignment work on the CCO-bending band is in progress, and the assignments for K=0andK=1(+and-) are included in this report. Accurate term values for the CCO-bending mode could be obtained. The results allowed the determination of the leading rotational constants for the trans-species in the excited vibrational state of the CCO-bending state. The complete known assigned lines of about 16,000 lines for the parent isotopomer and about 650 lines for 13 -C1 and 13−C2 (see graphical abstract) substituted Ethanol isotopomers are gathered in Appendix I and II, respectively. These atlases should be a valuable tool for further energy level analysis and astronomical detection of Ethanol in interstellar space.

Accurate and Efficient Schemes for Mapping Out Two Isolated Seams of Conical Intersections with Neural Networks Solely Based on Adiabatic Energies: A Case Study of H+ + NO(X2Π) → H + NO+(X1Σ+).

A new scheme in the neural network (NN) diabatization approach that solely utilizes the adiabatic energies for constructing the global diabatic potential energy matrices (PEMs) of the molecular systems with two isolated seams of conical intersections (CIs) is proposed. Taking a prototype charge transfer reaction H+ + NO(X2Π) → H + NO+(X1Σ+), where two seams of CIs are located at the different linear geometries N-O-H and O-N-H, for example, the diabatization with the new scheme including a diabatic state constraint is shown to map out the topographies of both two linear CIs with 100% of the success rate in 10 different trainings, while the diabatization without such constraint hardly represents CIs, in which the avoided crossings appear instead. Simultaneously, we propose a scheme to separate the whole reactive space into three different regions and define the minimal Euclidean distances for each region to efficiently sample the energy points for the NN trainings. Through adjusting the minimal Euclidean distances, the number of the adiabatic energy data needed in the construction of diabatic PEM can be heavily decreased, lowered from ∼2000 to ∼280 energy points, which is much less than the number (>22 000) of ab initio energy points used in earlier spline diabatic PEM. Further quantum dynamic calculations show that the reaction probabilities, vibrational state distributions, and vibrational state resolved differential cross sections are well reproduced on the new NN diabatic PEM, validating these schemes for constructing the diabatic PEM.

Constitutive modelling of a dry sand–structure interface under high-frequency vibration with a constant normal load

Sand–structure interfaces undergo strength loss and volume contraction under high-frequency vibration, potentially compromising the performance of underground structures in high-speed railway engineering. However, an appropriate method for quantitatively characterizing the behaviour of the sand–structure interface under high-frequency vibration is currently lacking, impeding the advancement of related design methods. In this work, the primary deformation and strength characteristics, such as the evolution of shear stress and volumetric strain, of the dry sand–structure interface under high-frequency vibration are summarized via a modified direct shear apparatus under a constant normal load. The concept of “vibro-induced virtual pore pressure” is subsequently introduced to modify the expressions of the critical state, yield, and bounding surfaces. The relationships between vibro-induced volume contraction and the vibration stress amplitude and state parameters are also established. Ultimately, a constitutive model describing the behaviour of the dry sand–structure interface under high-frequency vibration is formulated within the frameworks of critical state soil mechanics and bounding surface plasticity. The model comprises 14 parameters, all of which can be calibrated via laboratory experiments. Through comparison with experimental observations, the model is found to accurately simulate the key behaviours of the dry sand–structure interface under both static and high-frequency vibration conditions with a constant normal load, effectively reflecting the influence of the density, normal stress, and vibration stress amplitude of the sample.

Experimental investigation on heat transfer enhancement of supercritical pressure aviation kerosene in tubular laminar flow by vibration

In advanced aero-engine thermal management systems, aviation kerosene serving as a coolant unavoidably works in a vibration environment. In this article, the laminar heat transfer performance of Chinese aviation kerosene RP-3 flowing through a horizontal micro-tube under various vibration conditions at supercritical pressures was investigated experimentally. The effects of several impact factors such as system pressure, heat flux, mass flux, inlet temperature, vibration acceleration, and vibration frequency on the heat transfer enhancement were explored in a systematic manner. Experimental results indicate that: (i) the vibration could lead to intense thermal and momentum mixing among different boundary layers of tubular laminar flow and significantly strengthens the heat transfer, and the higher Re can lead to a stronger enhancement effect. The maximum observed HTER across all experimental data is 2.8, occurring at x/d = 224.1 with the inlet temperature of 373 K; (ii) HTER hardly changes with system pressures, exhibiting a maximum relative deviation of 3.9 % at different pressures. Heat transfer enhancement has a strong dependency on heat flux, as the heat flux increases from 36 kW/m2 to 108 kW/m2, the average HTC increased by up to 36.4 %; (iii) the HTC and HTER monotonically rise with increasing vibration acceleration. Peak values in HTC and HTER are observed at vibration frequencies of 625 Hz, 191 Hz, and 242 Hz; (iv) vibration has little impact on the thermal acceleration but noticeably weakens the buoyancy close to the outlet area at high heat flux. Two well-predicted correlations for the Nu in tubular laminar flow, one with vibration and one without, are proposed.

Machine learning-based classification of quality grades for concrete vibration behaviour

The vibration behaviour of the vibrating rods is one of the key factors for the quality of concrete vibration that is essential for the long-term safety of concrete structures. Although many vibration operation regulations have been widely applied, evaluating method for concrete vibration samples is relatively rare. To fill this gap, this paper proposes a concrete vibration data acquisition system and attempts to perform a quality analysis of samples employing machine learning that amalgamates various parameters. The experimental results demonstrate that the data collection system to identify the vibration state achieves an accuracy of 93.75% and an accuracy of 90.3% in classifying vibration quality levels. The proposed method can classify and evaluate concrete quality levels, which strongly supports the visualization of concrete vibration process and the implementation of autonomous robot vibration. In the future, improving the reliability of the system and enhancing the accuracy of algorithms will be the focused.

The mechanism of polygonal wheel wear considering a three-dimensional profile

Wheel polygonal wear is one of the most serious problems in the railway industry nowadays. To study the mechanism of wheel polygonal wear, the wear prediction model was established. The three-dimensional wheel profile model and the improved USFD wear prediction algorithm were used to research the wear state of the wheel. The vehicle system dynamic characteristics and wheel wear state under different running speeds are studied. The results show that the vibration state of the wheel will be affected by the vertical and lateral coupling vibration of the wheel when considering the three-dimensional wheel polygonal wear. Due to the influence of coupled vibration, the wheel will appear larger wheel-rail force fluctuation points at different phase angles. The large wheel-rail force fluctuation at these different phase angles is one of the reasons for the formation of wheel polygonal wear. At the same time, the natural mode of the vehicle system will also affect the order of the wheel polygon and the amplitude of the wheel polygon. This study provides a new idea for the research of the wheel polygon mechanism.

Atomic-Resolution Vibrational Mapping of Bilayer Borophene.

The successful synthesis of borophene beyond the monolayer limit has expanded the family of two-dimensional boron nanomaterials. While atomic-resolution topographic imaging has been previously reported, vibrational mapping has the potential to reveal deeper insight into the chemical bonding and electronic properties of bilayer borophene. Herein, inelastic electron tunneling spectroscopy (IETS) is used to resolve the low-energy vibrational and electronic properties of bilayer-α (BL-α) borophene on Ag(111) at the atomic scale. Using a carbon monoxide (CO)-functionalized scanning tunneling microscopy tip, the BL-α borophene IETS spectra reveal unique features compared to single-layer borophene and typical CO vibrations on metal surfaces. Distinct vibrational spectra are further observed for hollow and filled boron hexagons within the BL-α borophene unit cell, providing evidence for interlayer bonding between the constituent borophene layers. These experimental results are compared with density functional theory calculations to elucidate the interplay between the vibrational modes and electronic states in bilayer borophene.

Dynamic Interplay between the Mode-Randomization and Autodetachment of the Dipole-Bound States of the Anion.

State-specific dynamics of the dipole-bound state (DBS) of the cryogenically cooled deprotonated 4,4'-biphenol anion have been investigated by picosecond time-resolved pump-probe spectroscopy. For DBS vibrational states below the electron-detachment threshold, the relaxation rate is slow to give a lifetime (τ) longer than ∼5 ns, and it is attributed to the nonvalence-to-valence orbital transformation. For the DBS resonances above the detachment threshold, however, the lifetime decreases with the activation of autodetachment, whereas the otherwise zeroth DBS modes seem to be randomized by intramolecular vibrational energy redistribution (IVR), as manifested in the biexponential transients. As the DBS internal energy increases further, the lifetime shows a monotonic decrease to give τ ∼ 50 ps at E'vib ∼ 1700 cm-1. This study demonstrates that IVR may play an important role in the autodetachment dynamics when the density of states rapidly increases with increasing vibrational energy, giving important implications for the electron-transfer dynamics taking place in large biological or astrochemical systems.

Molecular insights into vibration-induced phase change dynamics of low-boiling-point refrigerant

Vibration-induced evaporation and boiling has attracted great attention due to its prominent efficiency. However, the understanding of low-boiling-point refrigerant phase change on various vibration and wettability conditions remains to be investigated. In this study, molecular dynamics simulations are performed to explore the vibration-induced phase change performance of R1336mzz(Z) nanofilm over a copper substrate. Results found that the phase change mode of R1336mzz(Z) nanofilm can be divided into diffusive evaporation, nucleate boiling, and film boiling/cavitation. For one thing, the residual ratio of R1336mzz(Z) molecules lies on the vibrational amplitude (A) and frequency (f), with a linear relation to Af3/2 when Af3/2 is less than 150. For another, the molecular motion is originated from joint action of thermal momentum and mechanical tensioning, leading to film boiling or cavitation by tunning the predominant mechanism. In addition, the impacts of interfacial wettability on vibration-induced phase change are discussed in terms of the heat transfer ability and potential barrier for bubble nucleation. Results reveal that hydrophilic surface causes strong attraction at near-wall region to increase heat transfer, while hydrophobic surface shows weak potential barrier, which promotes the occurrence of bubble nucleation. These findings deliver insights to broad the use of high-frequency vibration in industrial applications.

Symmetry properties, tunneling splittings of some vibrational energy levels and torsional IR spectra of the trans – and cis – conformers of hydroquinone molecule

Torsional vibrational states of trans − and cis − conformers belonging to point symmetry groups C2H and C2V, respectively, of hydroquinone molecules are classified according to the irreducible representations of the molecular symmetry group D2H(M). A correspondence has been established between the symmetry elements of the D2H(M) group and the symmetry elements on the torsional coordinate plane for two-dimensional surfaces of potential energy, wave functions, kinetic coefficients and dipole moment projections. A correspondence has been established between the symmetry species of the point symmetry groups C2H, C2V and the symmetry species of the molecular symmetry group D2H(M). Conformational states, barriers to internal rotation and the above-mentioned characteristics of the hydroquinone molecule were calculated at the MP2/Aug-cc-pVDZ, MP2/Aug-cc-pVQZ, MP2/Aug-cc-pVTZ, MP2/CBS(aD,aT,aQ), and CCSD(T)/dAug-cc-pVDZ levels of theory. The calculated data sets were approximated using symmetry-adapted sets of basis functions. Using a numerical solution of the vibrational Schrödinger equation of restricted dimensionality, the energies and wave functions of 50 stationary torsional states of the hydroquinone molecule were determined for the first time. The values of tunneling splittings of the ground vibrational and a number of excited torsional states of trans − and cis − conformers were determined. In particular, when calculating at the MP2/CBS(aD,aT,aQ) level of theory, the values of tunneling splittings of the ground vibrational states of trans − and cis − conformers turned were 1.32*10-6 and 1.62*10-6 cm−1, which is consistent with the experimentally established upper limit for this value in the cis − conformer by authors of [W. Caminati, S. Melandri, L. B. Favero, J.Chem.Phys., 100 (1994) 8569 – 8572] (0.2 MHz or 6.67*10-6 cm−1). The calculations of the matrix elements of the dipole moment operator and the partition function made it possible to simulate the torsional IR spectra of the molecule’s conformers at different temperatures. The frequencies of fundamental torsional vibrations in the trans – (267.1 and 269.0 cm−1) and cis – (269.5 and 270.9 cm−1) conformers, calculated at the MP2/CBS(aD,aT,aQ) level of theory, are in good agreement with the experimental value of frequency of this vibration (266 cm−1), established in [W.G. Fateley, G.L. Carlson, F.F. Bentley, J.Phys.Chem., 79 (1975) 199–204.].

Behavior of circular ultra-high-strength concrete-filled steel tube columns subjected to combined high-axial and cyclic lateral loads

The present study examined the seismic performance of circular concrete-filled steel tube (CFST) columns infilled with ultra-high-strength concrete (UHSC >100 MPa) as well as the beneficial effect of embedded spiral confining (SC) reinforcement at high axial load ratios (0.53–0.70) in order to enhance the safety and structural integrity of high-rise buildings. Seven specimens, including four CFST columns and three SC-CFST columns, were investigated under combined high axial and quasi-static cyclic lateral loads. The test parameters included axial load ratio (0.53–0.70), concrete compressive strength (64–111 MPa), embedded spiral confining reinforcement (pitch of 30 mm and 60 mm), and concrete vibration state. The test results demonstrated that adding spiral reinforcement improved the deformation capacity of CFST columns, which was reduced by the increased concrete strength. By embedding spiral confining reinforcement (volumetric ratio 3.3 %), the SC-CFST columns attained a deformation capacity comparable to that of CFST columns with normal concrete (64 MPa) for an axial load ratio of 0.53. The higher axial load ratio and concrete strength of composite columns led to a significant P-Delta moment effect, resulting in a substantial drop in columns' lateral load capacity. Composite columns with UHSC showed a larger contribution from the column base rotation to the specimen's lateral deformation when compared to composite columns with normal-strength concrete because the rigidity offered by UHSC made the column more rigid and reduced its flexural deformation. The unvibrated core concrete of the CFST column did not influence the initial stiffness and energy dissipation capacity. However, during the later stages of loading, the damage in core concrete rapidly accumulated, resulting in instant degradation of the load capacity and stiffness, considerable axial shortening, and poor deformation capacity. The experimental investigation offered a reliable reference on the performance of CFST columns constructed under high-axial load ratios (0.53–0.7) using ultra-high-strength concrete (>100 MPa) and spiral confining reinforcement so as to promote their application in practical engineering.

Vibration-induced wall–bubble interactions under zero-gravity conditions

This work is devoted to a theoretical and numerical study of the dynamics of a two-phase system vapour bubble in equilibrium with its liquid phase under translational vibrations in the absence of gravity. The bubble is initially located in the container centre. The liquid and vapour phases are considered as viscous and incompressible. Analysis focuses on the vibrational conditions used in experiments with the two-phase system SF $_6$ in the MIR space station and with the two-phase system para-Hydrogen (p-H $_2$ ) under magnetic compensation of Earth's gravity. These conditions correspond to small-amplitude high-frequency vibrations. Under vibrations, additionally to the forced oscillations, an average displacement of the bubble to the wall is observed due to an average vibrational attraction force related to the Bernoulli effect. Vibrational conditions for SF $_6$ correspond to much smaller average vibrational force (weak vibrations) than for p-H $_2$ (strong vibrations). For weak vibrations, the role of the initial vibration phase is crucial. The difference in the behaviour at different initial phases is explained using a simple mechanical model. For strong vibrations, the average displacement to the wall stops when the bubble reaches a quasi-equilibrium position where the resulting average force is zero. At large vibration velocity amplitudes this position is near the wall where the bubble performs only forced oscillations. At moderate vibration velocity amplitudes the bubble average displacement stops at a finite distance from the wall, then large-scale damped oscillations around this position accompanied by forced oscillations are observed. Bubble shape oscillations and the parametric resonance of forced oscillations are also studied.

(Sensor Division Student Research Award) Ultra-Sensitive Photothermal Spectroscopy for Attogram-Level Detection

Molecular-level spectroscopy is crucial for sensing and imaging applications, yet detecting and quantifying minuscule quantities of chemicals remains a challenge, especially when they surface-adsorb in low numbers. Here, we introduce a photothermal spectroscopic technique that enables high selectivity sensing of adsorbates with an attogram detection limit. Our approach utilizes the Seebeck effect in a microfabricated nanoscale thermocouple junction, incorporated into the apex of a microcantilever. We observe minimal thermal mass exhibited by the sensor which maintains exceptional thermal insulation. The temperature variation driving the thermoelectric junction arises from the non-radiative decay of molecular adsorbates' vibrational states on the tip. We demonstrate the detection of photothermal spectra of physisorbed trinitrotoluene (TNT) and dimethyl methylphosphonate (DMMP) molecules, as well as representative polymers, with an estimated mass of 10-18 g. Figure 1