Excited Bending Research Articles

High resolution infrared spectroscopy of H 12C 13CD and H 13C 12CD: The bending states up to v4 + v5 = 2

The high-resolution infrared spectrum of two partially deuterated isotopologues of acetylene, H 12C 13CD and H 13C 12CD, has been recorded by Fourier transform spectroscopy in the range 450–1850 cm −1. The bending fundamental bands and a number of overtone, combination and hot bands have been identified for both isotopomers. In total, 17 vibrational bands for H 12C 13CD and 18 bands for H 13C 12CD were analyzed, involving all the l-vibrational components of the excited bending states up to ν t = ν 4 + ν 5 = 2. The data pertaining to each molecule were analyzed together with the pure rotational transitions recorded in the millimeter- and sub-millimeter-wave frequency ranges and the ν 5 ← ν 4 band available in the literature. The model Hamiltonian adopted for the analysis takes into account the usual vibration and rotation l-type resonances. The ground state and 9 vibrationally excited states have been characterized for each isotopomer. The spectroscopic parameters obtained from the fits reproduce 1617 transitions for H 12C 13CD and 1613 transitions for H 13C 12CD, with standard deviations of the fit equal to 0.00038 cm −1 and 0.00032 cm −1, respectively.

Complete experimental rovibrational eigenenergies of HCN up to 6880 cm−1 above the ground state

The [H,C,N] molecular system is a very important model system to many fields of chemical physics and the experimental characterization of highly excited vibrational states of this molecular system is of special interest. This paper reports the experimental characterization of all 3822 eigenenergies up to 6880 cm(-1) relative to the ground state in the HCN part of the potential surface using high temperature hot gas emission spectroscopy. The spectroscopic constants for the first 71 vibrational states including highly excited bending vibrations up to v(2) = 10 are reported. The perturbed eigenenergies for all 20 rotational perturbations in the reported eigenenergy range have been determined. The 11,070 eigenenergies up to J = 90 for the first 123 vibrational substates are included as supplement to this paper. We show that a complete ab initio rovibrational analysis for a polyatomic molecule is possible. Using such an analysis we can understand the molecular physics behind the Schrödinger equation for problems for which perturbation theoretical calculations are no more valid. We show that the vibrational structure of the linear HCN molecule persists approximately up to the isomerization barrier and only above the barrier the accommodation of the vibrational states to the double well structure of the potential takes place.

Communication: Determination of the bond dissociation energy (D) of the water dimer, (H2O)2, by velocity map imaging

The bond dissociation energy (D(0)) of the water dimer is determined by using state-to-state vibrational predissociation measurements following excitation of the bound OH stretch fundamental of the donor unit of the dimer. Velocity map imaging and resonance-enhanced multiphoton ionization (REMPI) are used to determine pair-correlated product velocity and translational energy distributions. H(2)O fragments are detected in the ground vibrational (000) and the first excited bending (010) states by 2 + 1 REMPI via the C̃ (1)B(1) (000) ← X̃ (1)A(1) (000 and 010) transitions. The fragments' velocity and center-of-mass translational energy distributions are determined from images of selected rovibrational levels of H(2)O. An accurate value for D(0) is obtained by fitting both the structure in the images and the maximum velocity of the fragments. This value, D(0) = 1105 ± 10 cm(-1) (13.2 ± 0.12 kJ/mol), is in excellent agreement with the recent theoretical value of D(0) = 1103 ± 4 cm(-1) (13.2 ± 0.05 kJ∕mol) suggested as a benchmark by Shank et al. [J. Chem. Phys. 130, 144314 (2009)].

Rovibrational eigenenergy structure of the [H,C,N] molecular system

The vibrational-rotational eigenenergy structure of the [H,N,C] molecular system is one of the key features needed for a quantum mechanical understanding of the HCN⇌HNC model reaction. The rotationless vibrational structure corresponding to the multidimensional double well potential energy surface is well established. The rotational structure of the bending vibrational states up to the isomerisation barrier is still unknown. In this work the structure of the rotational states for low and high vibrational angular momentum is described from the ground state up to the isomerisation barrier using hot gas molecular high resolution spectroscopy and rotationally assigned ab initio rovibronic states. For low vibrational angular momentum the rotational structure of the bending excitations splits in three regions. For J < 40 the structure corresponds to that of a typical linear molecule, for 40 < J < 60 has an approximate double degenerate structure and for J > 60 the splitting of the e and f components begins to decrease and the rotational constant increases. For states with high angular momentum, the rotational structure evolves into a limiting structure for v(2) > 7--the molecule is locked to the molecular axis. For states with v(2) > 11 the rotational structure already begins to accommodate to the lower rotational constants of the isomerisation states. The vibrational energy begins to accommodate to the levels above the barrier only at high vibrational excitations of v(2) > 22 just above the barrier whereas this work shows that the rotational structure is much more sensitive to the double well structure of the potential energy surface. The rotational structure already experiences the influence of the barrier at much lower energies than the vibrational one.

The ν1 band system of HCN

The emission spectrum of HCN has been recorded at 1463 K using hot gas molecular emission (HOTGAME) spectroscopy in the wavenumber region of 2900–3500 cm −1 with a resolution of 0.01 cm −1. The dense emission spectrum was analyzed with the spectrum analysis software SyMath™ implemented in the Mathematica™ computer algebra system. This work reports the analysis of the 1 v 2 l 0 → 0 v 2 l 0 band series up to v 2 = 8 and of the 1 v 2 l 1 → 0 v 2 l 1 band series up to v 2 = 6.36 rovibronic ( v 1, v 2, l, e/ f, v 3) substates of HCN including all l = 0, 2, 4, 6, 8 sublevels of the v 1 v 2 l v 3 = 18 l 0 highly excited bending combination mode have been characterized for the first time and for the 22 known vibrational sublevels it was possible to improve the existing spectroscopic constants substantially. 18 ( v 1, v 2, l, v 3) vibrational sublevels are located for the first time relative to the 00 00 state. The analysis reported here includes rovibrational states up to very large rotational excitations of J = 60–80. For the 1 v 2 l 0 combination states the rotational states have been determined up to J = 86 which corresponds to 7000 cm −1 rotational excitation energy, this state is only 2000 cm −1 below the isomerization barrier. It was possible to determine for the first time the L v high order rotational constant for many states reported in this work.

A review of noise control methods for composite structures.

Composite materials and structures offer great promise to all air vehicles and are being increasingly considered for lightweight advanced applications. However, composite structures are efficient radiators of noise mainly due to excitation and propagation of supersonic bending and/or shear waves in the structures. Composite skin-stringer structures mostly support supersonic flexural or bending waves propagating in the laminated structure whereas noise radiation by sandwich structures is dominated by supersonic shear waves in the core. The vibro-acoustic behavior of sandwich composites has been studied by several investigators. Wave number diagrams have been useful in identifying supersonic flexural and shear waves in composite structures. It has been shown that the radiating wave number components increase with increasing plate stiffness, causing increased sound radiation. Although design criteria for sandwich composites in terms of sub-sonic core wave speeds have been evolved, skin-stringer composite structures must use added noise control treatments. Noise control of composite structures, thus, still presents a significant technical challenge as the main advantages afforded by these structures, such as low weight and high strength, must not be compromised by added treatments. This paper presents a review of recent advances in the noise control techniques for composite structures.

Acetylene, 12C 2H 2: Refined analysis of CRDS spectra around 1.52 μm

The analysis of CW-cavity ring down absorption spectra of 12C 2H 2 previously reported by Robert et al. (Mol. Phys. 106 (2008) 2581) was improved in the range 6667–7015 cm −1. Some 1825 lines were newly assigned. They either belong to 105 new sub-bands, involving 69 previously unreported sub-states, or extend assignments in 35 already known sub-bands. A global fit procedure of line positions from the full 12C 2H 2 database containing 18 415 lines, including those newly assigned, was performed, accessing vibrational states up to 8900 cm −1. Coriolis interactions were systematically introduced in the global Hamiltonian, which also accounted for higher order vibrational constants and considered the role of higher excited bending states than before. The dimensionless standard deviation of the fit was 1.07 and 396 effective vibration–rotation parameters were determined. Two local, interpolyad couplings were evidenced for the first time. A set of 121 new lines from 12CH 13CH present in natural abundance in the gas sample were also assigned.

H+ versus D+ transfer from HOD+ to CO2: Bond-selective chemistry and the anomalous effect of bending excitation

Reactions of HOD(+) with CO(2) have been studied for HOD(+) in its ground state, and with one quantum of excitation in each of its vibrational modes: (001)--predominantly OH stretch, 0.396 eV; (010)--bend, 0.153 eV; and (100)--predominantly OD stretch, 0.293 eV. Integral cross sections and product recoil velocities were recorded for collision energies from threshold to 3 eV. The cross sections for both H(+) and D(+) transfer rise with increasing collision energy from threshold to ∼1 eV, then become weakly dependent of the collision energy. All three vibrational modes enhance the total reactivity, but quite mode specifically. The H(+) transfer reaction is enhanced by OH stretch excitation, whereas OD stretch excitation has little effect. Conversely, the D(+) transfer reaction is enhanced by OD stretch excitation, while the OH stretch has little effect. Excitation of the bend strongly enhances both channels. The effects of the stretch excitations are consistent with previous studies of neutral HOD mode-selective chemistry, and can be at least qualitatively understood in terms of a late barrier to product formation. The fact that bend excitation produces the largest overall enhancement is surprising, because this is the lowest energy excitation, and is not obviously connected with the reaction coordinates for either H(+) or D(+) transfer. A rationalization in terms of the effects of water distortion on the potential surface is proposed.

High resolution slit-jet infrared spectroscopy of ethynyl radical: 2Π–2Σ+ vibronic bands with sub-Doppler resolution

High resolution infrared spectra for four (2)Π-(2)Σ(+) bands of jet-cooled ethynyl radical (i.e., C(2)H) in the gas phase are reported. The combination of (i) slit-jet cooling (T(rot) ≈ 12 K) and (ii) sub-Doppler resolution (≈ 60 MHz) permits satellite branches in each (2)Π-(2)Σ(+) band to be observed and resolved for the first time as well as help clarify a systematic parity misassignment from previous studies. The observed lines in each band are least squares fit to a Hamiltonian model containing rotational, spin-rotational, spin-orbit, and lambda-doubling contributions for the (2)Π state, from which we report revised excited state constants and band origins for the observed bands. Three of the four bands fit extremely well within a conventional (2)Π model (i.e., σ < 20 MHz), while one band exhibits a local perturbation due to an avoided crossing with a near resonant dark state. Vibronic assignments are given for the observed bands, with the dark state clearly identified as a highly excited stretch and bending overtone level X̃ (1,2(2),0) by comparison with high level ab initio efforts.

Research of a Ring-Type Linear Ultrasonic Motor

A new ring-type linear ultrasonic motor is proposed in this study. In this new design, bending vibration traveling wave is generated in a long ring by two groups of PZT ceramics bonded on the inner sides of the linear beams. Elliptical trajectory motions can be formed at particles on the teeth, which can realize the linear driving by frictional force. The working principle of the proposed design is introduced. Two bending vibration modes that have a phase difference of 90deg on space are analyzed. The elliptical motion trajectory of node on the tooth gained by the transient analysis verifies the excitation of bending traveling wave. A prototype motor is fabricated and measured, and a maximum speed of 15mm/s is reached.

A-1-2 磁気ディスク装置におけるコイル曲げ加振力の低減の検討(A-1 HDD,口頭発表:情報機器コンピュータメカニクス)

A-1-2 磁気ディスク装置におけるコイル曲げ加振力の低減の検討(A-1 HDD,口頭発表:情報機器コンピュータメカニクス)

Temperature dependence of vibrational relaxation of the OH bending excitation in liquid H 2O

Mid-infrared pump–probe spectroscopy measurements of the OH bending vibration in pure liquid water were performed at different temperatures. The population lifetime increases from 170 ± 15 fs at T = 295 K to 250 ± 15 fs at T = 348 K. This temperature dependence can be explained by the decrease in the spectral overlap between the OH bending and the high-frequency librational modes, supporting the relaxation scenario that the bend vibrational energy is dominantly transferred to librational motions. It was also found that the temperature dependence becomes absent below room temperature, the possible origin for which is discussed.

Bending-induced diminution of shape resonances in the core-level absorption region of hot CO2 and N2O

We have measured the initial vibrational-state-specific, symmetry-resolved ion-yield spectra of CO2 and N2O in the shape resonance regions above the K-shell ionization thresholds. For both molecules, significant diminution of the shape resonances by bending excitation in the initial electronic ground state is observed. The measured ion-yield spectra are well reproduced by calculations employing the Schwinger variational principle. The observed changes in the spectra are seen to be due to a shift of the resonances to lower energy and an initial increase in width with bending.

High sensitivity ICLAS of H 218O in the 12,580–13,550 cm −1 transparency window

High-sensitivity Intracavity Laser Absorption Spectroscopy (ICLAS) is used to measure the high resolution absorption spectrum of H 2 18O between 12,580 and 13,550 cm −1. This spectral region covers the 3 v+ δ polyad of very weak absorption. Four isotopologues of water (H 2 18O, H 2 16O, H 2 17O, HD 18O) are found to contribute to the observed spectrum. Spectrum analysis is performed with the aid of variational calculations and allowed for assigning 1126 lines belonging to H 2 18O, while only 160 H 2 18O lines are included in the HITRAN-2008 database. Altogether, 823 accurate energy levels of H 2 18O are determined from transitions attributed to 26 upper vibrational states, 438 of them being reported for the first time. New information includes energy levels of four newly observed vibrational states of H 2 18O: (2 4 0), (1 4 1), (0 4 2) and (2 3 1) at 13,167.718, 13,212.678, 13,403.71 and 15,073.975 cm −1, respectively. H 2 18O transitions involving highly excited bending states like (1 6 0), (0 6 1), (0 7 1), (1 7 0), (0 9 0) and even (0 10 0) have been identified as a result of an intensity borrowing from stronger bands via high-order resonance interactions. Thirty-six new energy levels of H 2 17O, present with a 2% relative concentration in our sample, could be determined. The rotational structure of the (0 2 3) state of HD 18O at 13,245.497 cm −1 is also reported for the first time.

Complete experimental rovibrational eigenenergies of HNC up to 3743cm−1 above the ground state

The [H,C,N] system is one of the ideal candidate molecules to test new models aimed to calculate the manifold of the rotational, vibrational, and electronic states of a triatomic molecule. The isomerization reaction HCN⇌HNC is one of the most important model systems for the study of unimolecular reactions. This paper reports on the experimental characterization of all 1191 eigenenergies up to 3743 cm(-1) relative to the ground state in the HNC part of the potential surface using high temperature hot gas emission spectroscopy. The spectroscopic constants for the first 27 vibrational states including highly excited bending vibrations up to v(2) = 7 are reported. The first 14 rotational perturbations have been identified and the perturbed eigenenergies were determined. The 3200 eigenenergies up to J = 70 for the first 47 vibrational substates are included as supplement to this paper.

Chemical Dynamics Simulations of CO2in the Ground and First Excited Bend States Colliding with a Perfluorinated Self-Assembled Monolayer

Energy transfer in collisions of CO2, in the ground (0000) state and first excited (0110) bend state, with a perfluorinated alkanethiol self-assembled monolayer (F-SAM) was studied by quasiclassical trajectory simulations employing a united-atom (UA) model to represent the F-SAM. The CO2 molecule was aimed perpendicularly to the surface at incident energies of 1.6 and 10.6 kcal/mol. The exchange of bend energy is more efficient for penetrating trajectories while almost no energy exchange was found for direct trajectories. Bend energy transfer depends on the surface residence time (τ). In particular, the average bend energy of the scattered CO2 molecules increases linearly with τ for CO2(0000) + F-SAM, and it decreases linearly for CO2(0110) + F-SAM at both incident energies. For the highest collision energy, the average bend energy of the scattered CO2 molecules also increases linearly with the angle formed between the molecular axis and the axis perpendicular to the surface in CO2(0000) + F-SAM collision...

Communication: Experimental and theoretical investigations of the effects of the reactant bending excitations in the F+CHD3 reaction

The effects of the reactant bending excitations in the F+CHD(3) reaction are investigated by crossed molecular beam experiments and quasiclassical trajectory (QCT) calculations using a high-quality ab initio potential energy surface. The collision energy (E(c)) dependence of the cross sections of the F+CHD(3)(v(b)=0,1) reactions for the correlated product pairs HF(v('))+CD(3)(v(2)=0,1) and DF(v('))+CHD(2)(v(4)=0,1) is obtained. Both experiment and theory show that the bending excitation activates the reaction at low E(c) and begins to inactivate at higher E(c). The experimental F+CHD(3)(v(b)=1) excitation functions display surprising peak features, especially for the HF(v(')=3)+CD(3)(v(2)=0,1) channels, indicating reactive resonances (quantum effects), which cannot be captured by quasiclassical calculations. The reactant state-specific QCT calculations predict that the v(5)(e) bending mode excitation is the most efficient to drive the reaction and the v(6)(e) and v(5)(e) modes enhance the DF and HF channels, respectively.

Mode-specific reactivity ofCH4onPt(110)−(1×2): The concerted role of stretch and bend excitation

The state-resolved reaction probability of CH4 on Pt(110)−(1×2) was measured as a function of CH4 translational energy for four vibrational eigenstates comprising different amounts of C-H stretch and bend excitation. Mode-specific reactivity is observed both between states from different polyads and between isoenergetic states belonging to the same polyad of CH4. For the stretch/bend combination states, the vibrational efficacy of reaction activation is observed to be higher than for either pure C-H stretching or pure bending states, demonstrating a concerted role of stretch and bend excitation in C-H bond scission. This concerted role, reflected by the nonadditivity of the vibrational efficacies, is consistent with transition state structures found by ab initio calculations and indicates that current dynamical models of CH4 chemisorption neglect an important degree of freedom by including only C-H stretching motion.

Renner-Teller Effect, Spin−Orbit Coupling, and Fermi Resonance in BrCN+ (X̃2Π): A Combined Experimental and Theoretical Study

The spin-vibronic energy levels of BrCN(+) (X̃(2)Π) up to 7700 cm(-1) above the vibrational ground state have been measured using zero-kinetic energy photoelectron spectroscopy (ZEKE) and tunable coherent extreme ultraviolet (XUV) light. The fundamental bands for C≡N stretching, Br-C≡N bending, and C-Br stretching vibrations have been measured, and a strong bending excitation was observed. The Renner-Teller effect and the Fermi interaction between the C-Br stretching and the Br-C≡N bending have been observed experimentally. To characterize the spin-vibronic interaction in BrCN(+) (X̃(2)Π), an effective diabatic model Hamiltonian with spectroscopic parameters describing these interactions was used to calculate the vibronic energy levels. The spectroscopic parameters have been determined by fitting the experimental data. Theoretical calculations based on the diabatic model were also performed. The theoretical spectroscopic parameters have been calculated using the potential energy surfaces reported by Biczysko and Tarroni (Chem. Phys. Lett. 2005, 415, 223). The calculated vibronic energy levels and spectroscopic parameters have been compared with those from the experimental data. For the diabatic potential energy matrix, the ab initio calculations provide good description of the diagonal elements, however, the off-diagonal elements deviate appreciably from those determined by experimental data. By analyzing the ZEKE spectrum of the ground vibrational band, the first adiabatic ionization energy for BrCN has been determined as 95 675.5 ± 2.0 cm(-1).

Physics of Cellular Movements

The survival of cells depends on perpetual active motions, including (a) bending excitations of the soft cell envelopes, (b) the bidirectional transport of materials and organelles between the cell center and the periphery, and (c) the ongoing restructuring of the intracellular macromolecular scaffolds mediating global cell changes associated with cell adhesion locomotion and phagocytosis. Central questions addressed are the following: How can this bustling motion of extremely complex soft structures be characterized and measured? What are the major driving forces? Further topics include (a) the active dynamic control of global shape changes by the interactive coupling of the aster-like soft scaffold of microtubules and the network of actin filaments associated with the cell envelope (the actin cortex) and (b) the generation of propulsion forces by solitary actin gelation waves propagating within the actin cortex.