Ground Vibrational Research Articles

The 235-360 GHz Rotational Spectrum of 1-Oxaspiro[2.5]octa-4,7-dien-6-one─Analysis of the Ground Vibrational State and Its 10 Lowest-Energy Vibrationally Excited States.

The millimeter-wave rotational spectrum of 1-oxaspiro[2.5]octa-4,7-dien-6-one (1) was collected from 235 to 360 GHz. With the rotational spectrum of this compound available for the first time, more than 5500 a- and c-type transitions were observed and assigned for the vibrational ground state. These transitions were least-squares fit to S- and A-reduced, sextic distorted-rotor Hamiltonians in the Ir representation (σfit = 37 kHz). Additionally, transitions of four fundamental states (ν22, ν21, ν39, and ν38), four overtone states (2ν22, 3ν22, 4ν22, and 5ν22), and two combination states (ν22 + ν21 and ν22 + ν39) were measured, assigned, and least-squares fit to single-state, S- and A-reduced, sextic distorted-rotor Hamiltonians in the Ir representation (σfit < 42 kHz). The computed vibration-rotation interaction constants (B0 - Bv) (MP2 and B3LYP/6-311+G(2d,p)) were compared to their corresponding experimental values, showing excellent agreement for all fundamental states. Based on the intensities of the transitions from six members of the v ν22 series, the fundamental frequency of ν22 was determined to be 79.0 (2.1) cm-1.

Franck–Condon Factors in Electronic Excitations from the Ground and Excited Vibrational States Are Different

Franck–Condon Factors in Electronic Excitations from the Ground and Excited Vibrational States Are Different

Numerical investigations on influences of tunnel differential settlement on saturated poroelastic ground vibrations and lining forces induced by metro train

The influences of the tunnel settlement on vibrations of the saturated poroelastic ground and on the additional forces of the tunnel lining are investigated numerically in this paper. A three-dimensional finite element model incorporating the metro train, the tunnel lining and the saturated ground has been established. The ground settlement is introduced into the computational model by a specifically developed vehicle-rail interaction (VRI) element, through which the metro train can be dynamically coupled to the track. The ground is considered as a saturated poroelastic medium that is discretized by a self-developed saturated-soil element based on Biot's theory. Moreover, at truncation boundaries of the ground model, an absorbing boundary condition termed multi-transmitting formula (MTF) that is specially developed for the saturated soil element is applied to meet the far-filed radiation condition. With the inputs of ground settlement data from in-situ measurement, amplifications in the ground vibration and the lining forces have been quantitatively determined by comparing to the settlement-free case. It is found that the ground vibrational velocity and acceleration can reach 40–60 times the responses when there is no differential settlement of the tunnel; the dynamic internal forces including the axial force, the shear force and the bending moment of the tunnel lining can be 7–20 times higher than their static counterparts. • The ground vibrational velocity and acceleration can be as high as 40–60 times the responses when there is no differential settlement of the tunnel. • The differential settlement of the tunnel has negligible influence on the vibration amplification zone at the ground surface. • The differential settlement of the tunnel not only induce static internal forces to the lining structure, but also prompt the wheel/rail interaction and considerably amplify the dynamic internal forces of the lining.

Investigation of Sensors & Actuators based on Hankel Singular Values

The work presented here proposes a method to rank the efficiency of the actuators and sensors for the attenuation of excited structural modes. Aeroelastic wing designed with multiple control surfaces and equipped with sensors at different locations is used as a test case. A unifying theme to this work is the application of Hankel Singular Values (HSV), an analytical approach applied to the experimental data conducted during the Ground Vibrational (GVT) and Wind Tunnel (WT) tests. Modal information gathered from experimental results is used to define actuator/sensor relationships, once the mode of interest is decided then the sensor and actuator location is determined to effectively cater the structural vibrations, it paves the way for the design of specific performance metrics. The research will add redundancy to the available set of instrumentation by paving the way for the dedicated use of control surface for the stable flight mechanics or flight dynamics instability. The results presented here are supported by Power Spectral Densities (PSD’s) and band pass filters.

Dynamic characteristics and damage recognition of blast-induced ground vibration for natural gas transmission pipeline and its integrated systems

Abstract Natural gas pipeline network is a highly integrated network that moves natural gas throughout the continental and global services. Pipelines play a major role for the onshore and offshore gas transport, maintaining the record levels built up in recent years. However, once a rupture appears on a pipeline, the consequences of blast-induced incidents can pose a deadly threat in the vicinity of the failure location. Blast-induced ground vibration is the most significant impact that can seriously affect the surrounding parallel pipelines. In the present study, an experiment combined with a numerical investigation on the effect of blast-induced ground vibration of gas pipeline was undertaken. Dynamic characteristics such as peak vibration velocity, ground vibration acceleration, frequency response of blast-induced ground vibration were analyzed. Further, the modified prediction equations for blast-induced ground vibrational characteristics with distance were proposed. Ultimately, blast-induced displacement with the parallel pipeline was simulated, with a focus on risk vulnerability of gas pipeline. The main purpose of this paper is to facilitate a better understanding of the mechanical systems and dynamic characteristics governing the blast-induced ground vibration when the gas pipeline bursts, which is expected to be reliable for the safety spacing of buried integrated pipeline systems.

Determining the Parameters of the Ground Vibrational State of the NH2D and NHD2 Molecules

The object of the present investigation is the ammonia molecule the knowledge of the properties of which is important for solving numerous problems of astrophysics, physics, and chemistry of atmospheres of Earth, planets of the solar system, and exoplanets, nondestructive testing, and many other problems of science and technology. The parameters of the ground vibrational state of the NH2D and NHD2 molecules are determined.

Dynamics of ground and excited state vibrational relaxation and energy transfer in transition metal carbonyls.

Nonlinear vibrational spectroscopy provides insights into the dynamics of vibrational energy transfer in and between molecules, a crucial phenomenon in condensed phase physics, chemistry, and biology. Here we use frequency-domain 2-dimensional infrared (2DIR) spectroscopy to investigate the vibrational relaxation (VR) and vibrational energy transfer (VET) rates in different solvents in both the electronic ground and excited states of Re(Cl)(CO)3(4,4'-diethylester-2,2'-bipyridine), a prototypical transition metal carbonyl complex. The strong C≡O and ester C═O stretch infrared reporters, located on opposite sides of the molecule, were monitored in the 1600-2100 cm(-1) spectral region. VR in the lowest charge transfer triplet excited state ((3)CT) is found to be up to eight times faster than in the ground state. In the ground state, intramolecular anharmonic coupling may be solvent-assisted through solvent-induced frequency and charge fluctuations, and as such VR rates are solvent-dependent. In contrast, VR rates in the solvated (3)CT state are surprisingly solvent-insensitive, which suggests that predominantly intramolecular effects are responsible for the rapid vibrational deactivation. The increased VR rates in the excited state are discussed in terms of intramolecular electrostatic interactions helping overcome structural and thermodynamic barriers for this process in the vicinity of the central heavy atom, a feature which may be of significance to nonequilibrium photoinduced processes observed in transition metal complexes in general.

Microwave Spectrum, r0 Structure, Dipole Moment, Barrier to Internal Rotation, and Ab Initio Calculations for Fluoromethylsilane

The microwave spectra of seven isotopomers of fluoromethylsilane, CH(2)FSiH(3), in the ground vibrational state were measured and analyzed in the frequency range 18-40 GHz. The rotational and centrifugal distortion constants were evaluated by the least-squares treatment of the observed frequencies of a- and b-type R- and b-type Q-transitions. The values for the components of the dipole moment were obtained from the measurements of Stark effects from both a- and b-type transitions and the determined values are: |mu(a)| = 1.041(5), |mu(b)| = 1.311(6), and |mu(t)| = 1.674(4) D. Structural parameters have been determined and the heavy atom distances (r(0)) in Angstroms are: Si-C = 1.8942(57) and C-F = 1.4035(55) and the angle in degree, angleSiCF = 109.58(14). A semi-experimental r(e) structure was also determined from experimental ground state rotational constants and vibration-rotation constants derived from ab initio force fields. The internal torsional fundamental, SiH(3), was observed at 149.2 cm(-1) with two accompanying hot bands at 138.8 and 127.5 cm(-1). The barrier to internal rotation was obtained as 717.3(16) cm(-1) (2.051(46) kcal mol(-1)) by combining the analysis of the microwave A and E splittings and the torsional fundamental and hot band frequencies. Ab initio calculations have been carried out with full electron correlation by the second-order perturbation method with several different basis sets up to MP2/6-311+G(d,p) to obtain geometrical parameters, barriers to internal rotation, and centrifugal distortion constants. Adjusted r(0) structural parameters have been obtained by combining the ab initio MP2/6-311+G(d,p) predicted values with the determined rotational constants for the fluoride as well as with the previously reported microwave data for the chloro- and bromo- compounds. These experimental results are compared to the corresponding parameters for the carbon analogues.

Millimeter-Wave Rotational Spectrum of CF3CCD in the Ground and Excited Vibrational States v10 = 1

Abstract Millimeter-wave rotational spectra of the symmetric top molecule CF3CCD have been measured in its ground and excited vibrational states, v10 = 1. Analysis of the ground-state spectra gave the following rotational parameters: B0 = 2696.06753 MHz, DJ = 0.22759 kHz, DJk = 6.1748 kHz. HJk (16.1 mHz) and HkJ (−0.243 mHz) were determined for the first time. In the v10 = 1 state, l = ±1 series have been assigned and spectroscopic parameters were obtained accurately: B1 = 2701.26211 MHz, qt+(2,2) = 3.30887 MHz, Aζ = 3263.93 MHz. The off diagonal parameter rt (0.152 MHz) was determined for the first time.

Measurements of acoustic and seismic pulses from outdoor explosions

Measurements of the ground vibrations produced by airborne detonations of C4 were conducted at locations with a variety of ground types, including concrete, soil, forest, tropical vegetation, and snow cover. The measurements show that, although two separate seismic (ground vibrational) arrivals can be detected in all cases, the early seismic arrival from an underground path is always much smaller than the vibration induced by the air blast arrival. The acoustic‐to‐seismic coupling ratio for the atmospheric wave is a constant with respect to distance and peak pressure at a given location, but varies from site to site, usually between 1 and 14 μm/s/Pa. A conservative empirical equation to predict ground vibration from explosions is derived. This equation predicts that the commonly used vibrational damage criteria of 12 and 25 mm/s will be exceeded when the peak positive pressure exceeds 480 Pa (147.6 dB) or 1 kPa (154.0 dB), respectively. Either of these levels is much higher than the Army overpressure damage criterion of 159 Pa (138 dB). Thus in most situations damage from blast overpressure will occur long before damaging levels of ground vibration are reached. [This research supported by the U.S. Army Corps of Engineers and SERDP Seed Project SI‐1410.]

A Combined Frequency Analysis of the ν3, ν9, 3ν4 and the Far-Infrared Bands of Ethane: A Reassessment of the Torsional Parameters for the Ground Vibrational State

The lowest frequency parallel fundamental band ν3 of ethane is Raman active. A stimulated Raman spectrum of the Q branch for this band at a resolution of 0.0055 cm−1 has been measured by D. Bermejo et al. (1992, J. Chem. Phys.97, 7055). The torsion–rotation series in this band with σ=3, where σ=0, 1, 2, and 3 labels the torsional sublevels, is perturbed by over 1 cm−1. The lowest frequency-degenerate fundamental ν9 is infrared active. A high-resolution (0.0014 cm−1) Fourier transform spectrum of this band has been measured by N. Moazzen-Ahmadi et al. (1999, J. Chem. Phys.111, 9609). The observed torsional splittings for this band are substantially larger than expected from the observed barrier height. Because of a near-degeneracy of the upper level in the ν9 band with its interacting partner (v9=0, v4=3) a perturbation allowed band 3ν4 has also been observed. We have carried out a combined analysis of ν3, ν9, and 3ν4 together with the far-infrared torsional spectra in the ground vibrational state (gs). A fit to within the experimental error was achieved using 37 parameters. The large torsional splittings in the ν9 band are attributed to Coriolis-type interactions between the torsional stacks of gs and v9=1 whereas the large shift for the torsion–rotation series with σ=3 in the ν3 band is attributed to Fermi-type interactions between the torsional stacks of the gs and v3=1. The introduction of the Fermi-type interactions causes a considerable change in the leading terms in the torsional Hamiltonian for the gs. These changes are quantitatively explained.

Restudy of the Ground Vibrational State of Hydrazine Using the Generalized IAM-like Treatment for the Amino-Wagging Tunneling Motion

The amino-wagging tunneling process in hydrazine was treated using the generalized IAM-like method developed by Hougen and Coudert, and Hamiltonian matrix elements were derived for each symmetry species in the combined group-theoretical and IAM-like treatment. Ground state microwave absorption transition data of hydrazine were least squares analyzed again in this treatment to determine axis switching angles for the amino-wagging tunneling process.

Resonance between the Ground Vibrational State and the Lowest Frequency Bending Mode of Thioketene

Far-infrared and mid-infrared spectra of thioketene have been recorded over the region 200–1250 cm−1and transitions assigned from the ν4, ν5, ν6, and ν9fundamentals and ν5+ ν9← ν9and ν5+ ν6← ν6hot bands. Ground state combination differences from ν4and ν5, together with ν6and ν9transitions, lower state combination differences from the ν5+ ν9← ν9and ν5+ ν6← ν6hot bands, and previous millimeter-wave data, have been included in a combined fit of ν6, ν9, and the ground state. The stronga-axis Coriolis interaction between ν6and ν9has been treated along with thec-axis centrifugal distortion interaction between ν9and the ground state. The magnitudes of these interactions are in agreement with values obtained fromab initiomolecular orbital calculations at the MP2/6-311G** and CCSD/6-311G** levels of theory.

ChemInform Abstract: Treatment of Tunneling Motions in Methylamine Using the Generalized IAM‐Like Method: Analysis of the Ground Vibrational State.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Investigation of the Ground Vibrational State of CD 3OH by a New "Ritz" Program for Direct Energy Level Fitting

The complete absorption spectrum of CD 3OH between 30 and 1200 cm −1 has been measured on the Bruker Fourier transform spectrometer of the Physical Chemistry Institute of the University of Giessen. In the present work we present the assignment of more than 20 000 lines between 30 and 850 cm −1, corresponding to transitions within the vibrational ground state of the molecule. These assignments have been performed with the help of a new computer program which evaluates the energies of the involved levels by the Rydberg-Ritz combination principle and can tackle such perturbations as Fermi-type resonances or Coriolis interactions. Up to now this program has evaluated the energies of 1789 levels belonging to A-type symmetry and of 2417 levels belonging to E-type symmetry, all in the vibrational ground state of the molecule. The evaluation of the energy level values allows comparisons between different isotopic species.

Treatment of Tunneling Motions in Methylamine Using the Generalized IAM-like Method: Analysis of the Ground Vibrational State

Hamiltonian matrix elements for the large-amplitude vibrational and rotational problem in methylamine (CH3NH2) are derived by using the generalized IAM-like method developed by Hougen and Coudert. Torsional-wagging-rotational energy differences (216) taken from far-infrared spectral data were analyzed using the Hamiltonian matrix derived to obtain axis-switching angles for the two dominant torsional-wagging tunneling processes.

ChemInform Abstract: The Electric Dipole and the Nuclear Quadrupole Moment of Methyl Bromide in the Ground Vibrational State.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The Electric Dipole and the Nuclear Quadrupole Moment of Methyl Bromide in the Ground Vibrational State

A set of high-resolution Stark measurements at millimeter-wave frequencies is reported for CH 3 79Br and CH 3 81Br. These results are analyzed together with previous data available in the literature to find new sets of molecular (rotational, hyperfine, and dipole moments) constants for both isotopic species. A particular improvement is obtained in the evaluation of the dipole moments, whose values are μ(79) = 1.82171 (26) 0, μ(8l) = 1.82185 (26) D, and for the hyperfine-structure parameters, which are estimated by assuming the most recent model for centrifugal distortion (M. R. Aliev and J. T. Hougen, J. Mol. Spectrosc. 106, 110-123 (1984)), obtaining eqQ 79 0 = 577.1088 (57) MHz, χ 79 J = −0.63 (16) kHz, χ 79 K = 12.6 (16) kHz and eqQ 81 0 = 482.1030 (94) MHz, χ 81 J = −0.57 (17) kHz, χ 81 K = 9.3 (22) kHz.

Rotational components of the v10 = 1 and ground vibrational levels of propyne with 13C substitutions for the frequency range 17–75 GHz

The microwave spectrum of 13C-substituted propyne was studied for the v 10 = 1 and ground vibrational states in the frequency range of 17 to 75 GHz for the naturally abundant species. Only a few of the ground vibrational components have been reported in the literature because of the weakness of the spectral lines. Those which have been reported were remeasured and the results presented for comparison with our own. The frequencies of 0 ≤ J ≤ 4 components were measured for naturally occurring 13C species and these frequencies were used to produce a constant set which can be used to predict overall frequencies of spectral components in the ground, v 10 = 1, 2 up to an accuracy of a few hundred kilohertz, thus enabling ready assignment of the quantum sets. Previously obtained experimental data for the ground vibration available from the literature and our own data for the ground and v 10 = 1 are presented and compared with the frequencies obtained from a comprehensive equation derived from perturbation techniques.

ChemInform Abstract: AB INITIO STUDIES ON THE GROUND STATE POTENTIAL SURFACE AND VIBRATIONAL SPECTRA OF NSF AND SNF

Chemischer InformationsdienstVolume 15, Issue 43 Physical Inorganic Chemistry ChemInform Abstract: AB INITIO STUDIES ON THE GROUND STATE POTENTIAL SURFACE AND VIBRATIONAL SPECTRA OF NSF AND SNF L. J. SCHAAD, L. J. SCHAADSearch for more papers by this authorB. A. JUN. HESS, B. A. JUN. HESSSearch for more papers by this authorP. CARSKY, P. CARSKYSearch for more papers by this authorR. ZAHRADNIK, R. ZAHRADNIKSearch for more papers by this author L. J. SCHAAD, L. J. SCHAADSearch for more papers by this authorB. A. JUN. HESS, B. A. JUN. HESSSearch for more papers by this authorP. CARSKY, P. CARSKYSearch for more papers by this authorR. ZAHRADNIK, R. ZAHRADNIKSearch for more papers by this author First published: October 23, 1984 https://doi.org/10.1002/chin.198443002Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume15, Issue43October 23, 1984 RelatedInformation