scholarly journals The C=O Stretching Frequency in the S1 (π* - n) State of Acetaldehyde and its Deuterated Derivatives Determined With the Photofragment Excitation Spectroscopy

1995 ◽  
Vol 15 (2-4) ◽  
pp. 249-259
Author(s):  
Takumi Kono ◽  
Masao Takayanagi ◽  
Ichiro Hanazaki
Keyword(s):  
Excitation Frequency ◽  
Laser Induced Fluorescence ◽  
Vibrational Structure ◽  
Supersonic Jets ◽  
Vibronic Structure ◽  
Formyl Radical ◽  
Out Of Plane ◽  
Dissociation Threshold ◽  
Excitation Techniques ◽  
Methyl Torsion

The vibrational structure was recorded for the S1 (π* - n) state of acetaldehyde (CH3CHO) and its deuterated derivatives (CH3CDO, CD3CHO and CD3CDO up to ∼3500 cm-1above the 0-0 bands with the LIF (laser induced fluorescence) and PHOFEX (photofragment excitation) techniques. In the PHOFEX spectroscopy, the yield of the formyl radical, HCO(X ˜) or DCO(X ˜), produced in the photodissociation of acetaldehyde is measured against the excitation frequency. The yield was determined by monitoring one of the rotational lines in the B˜ ← X˜ transition of the formyl radical by the LIF technique. This is the first measurement of the vibronic structure of acetaldehydes in supersonic jets above the dissociation threshold where they are non-fluorescent. The results have made it possible to locate v4 (the C=O stretching) and 2v4 bands unequivocally; the v4 fundamentals at 1217, 1189, 1210 and 1178 cm-1 above the 0-0 band for CH3CHO, CH3CDO, CD3CHO and CD3CDO, respectively. The corresponding overtone (2v4) bands are observed, respectively, at 2414, 2350, 2399 and 2334cm-1. All the vibronic bands newly observed in the PHOFEX spectra are found to be interpreted as the combinations of v4 and 2v4 with the modes appearing in the lower frequency (< 1200 cm-1) region, which consist of v10 (the C—C—O in-plane bending), v14 (the C=O out-of-plane wagging) and v15 (the methyl torsion).

scholarly journals Intermolecular Vibrations of the Complex of NO in the nsσ Rydberg States and Ar

1995 ◽  
Vol 15 (2-4) ◽  
pp. 157-165 ◽  
Author(s):  
Kazuhide Tsuji ◽  
Kazuhiko Shibuya ◽  
Kinichi Obi
Keyword(s):  
Excitation Spectrum ◽  
Multiphoton Ionization ◽  
Rydberg States ◽  
Intermolecular Forces ◽  
Vibrational Structure ◽  
Excitation Spectra ◽  
Van Der Waals Complex ◽  
Ionization Method ◽  
Dissociation Threshold ◽  
Intermolecular Vibrations

The resonance enhanced multiphoton ionization method has been applied to the study of NO-Ar van der Waals complex in the nsσ (n = 3,4) Rydberg states. We have assigned the intermolecular vibrations appearing in the ×X˜ excitation spectrum of the complex. The bending structure appeared only with the excitation of the stretching mode in the à state, which was interpreted by intermolecular forces. The E˜-à excitation spectra were independent of the initial intermolecular level in the à state and the dissociation threshold to NO(E2∑+ ) + Ar was determined to be 60950 cm-1. The s–d mixing in the 4sσ orbital would make the intermolecular vibrational structure in the E˜—Ãspectra complex.

Insights into the displacement field in magnetoelectric composites

2019 ◽  
Vol 31 (3) ◽  
pp. 436-444 ◽  
Author(s):  
George Youssef ◽  
Scott Newacheck ◽  
Louay S Yousuf
Keyword(s):  
Computational Models ◽  
Excitation Frequency ◽  
Interface Condition ◽  
Composite Cylinder ◽  
Sensors And Actuators ◽  
Interferometric Technique ◽  
Magnetoelectric Composite ◽  
Out Of Plane ◽  
Finite Element Package ◽  
Plane Displacement

The performance of strain-mediated magnetoelectric composite multiferroics hinges on the interface condition in both direct and converse coupling paradigms. The objective of this article is to report experimentally validated computational models of composite cylinder structure consisting of an outer piezoelectric cylinder mechanically attached to an inner magnetostrictive layer. Three contact conditions were computationally investigated, including bonding, no separation, and standard definitions from the used finite element package. The simulations were used to extract the harmonic, modal, and transient responses of the composite cylinder structure, which were compared to experimental work. Under the influence of an AC electric field, the in-plane and out-of-plane displacement maps were simultaneously measured using a noncontact interferometric technique. Results from the harmonic analysis were used to tune the material properties and boundary conditions used in all subsequent simulations, whereas the resonance frequency was in excellent agreement with the experiment. The modal analysis was validated by comparing a subset of the experimental and computational vibrational modes. Finally, the transient analysis was found to be in reasonable agreement with the experimental results with a focus on the response at the excitation frequency. The validated analysis framework can be used in the development of sensors and actuators based on composite multiferroics cylinder structures.

The visible absorption spectrum of 1,2-cyclobutanedione in the gas phase

1986 ◽  
Vol 64 (11) ◽  
pp. 2152-2161 ◽  
Author(s):  
R. A. Back ◽  
J. M. Parsons
Keyword(s):  
Absorption Spectrum ◽  
Gas Phase ◽  
Singlet State ◽  
Energy Levels ◽  
Vibrational Structure ◽  
Visible Absorption Spectrum ◽  
Excited Singlet ◽  
Bending Vibration ◽  
Visible Absorption ◽  
Out Of Plane

The visible absorption spectrum of 1,2-cyclobutanedione has been measured in the gas phase at wavelengths between 4000 and 5100 Å. The absorption is attributed to the allowed π* ← n+, 1B1 ← 1A1 transition corresponding to the first excited singlet state. The spectrum shows a complex well-resolved vibrational structure which has been analysed, with some 125 bands measured and assigned. The bands at the longer wavelengths show sharp rotational fine structure, not yet analysed. The strongest band in the spectrum at 4933 Å has been assigned as the 0–0 band, while a band almost as strong at 4820 Å is attributed to excitation of one quantum of [Formula: see text], the a2 out-of-plane carbonyl bending vibration, and it is suggested that this band owes its intensity to vibronic coupling. A number of symmetric vibrations are also excited in the spectrum, but with no long progressions. Sequence bands running to the blue with an interval of about 72 cm−1 are prominent throughout the spectrum, and are assigned to v13, the a2 ring-twisting vibration. Other hot bands were also observed involving v13 which permitted estimation of energy levels for this vibration both in the ground state and the excited state. The infrared spectrum was also measured and analysed in the gas phase between 600 and 4000 cm−1, and 14 bands were assigned to fundamental vibrations; some of these assignments, at the lower frequencies, are uncertain.

Laser-induced fluorescence from the predissociating formyl radical. 1. Mechanism for the predissociation of the A2A" state

1989 ◽  
Vol 93 (4) ◽  
pp. 1303-1307 ◽  
Author(s):  
G. Rumbles ◽  
J. J. Valentini ◽  
B. M. Stone ◽  
E. K. C. Lee
Keyword(s):  
Laser Induced Fluorescence ◽  
Formyl Radical

Vibronic structure in the far-UV electronic circular dichroism spectra of proteins

2015 ◽  
Vol 177 ◽  
pp. 329-344 ◽  
Author(s):  
Zhuo Li ◽  
David Robinson ◽  
Jonathan D. Hirst
Keyword(s):  
Circular Dichroism ◽  
Matrix Method ◽  
Vibrational Structure ◽  
Cd Spectra ◽  
Peptide Backbone ◽  
Electronic Circular Dichroism ◽  
Vibronic Structure ◽  
Far Ultraviolet ◽  
High Level ◽  
Circular Dichroïsm

The Franck–Condon effect is considered and the vibrational structure of the πnbπ* transition of the peptide backbone is incorporated into matrix method calculations of the electronic circular dichroism (CD) spectra of proteins in the far-ultraviolet. We employ the state-averaged CASPT2 method to calculate the ground and πnbπ* excited state geometries and frequencies of N-methylacetamide (NMA), which represents the peptide chromophore. The results of these calculations are used to incorporate vibronic levels of the excited states into the matrix method calculation. The CD spectra of a set of 49 proteins, comprising a range of structural types, are calculated to assess the influence of the vibrational structure. The calculated spectra of α-helical proteins are better resolved using the vibronic parameters and correlation between the experimental and the calculated intensity of less regular β structure proteins improves over most wavelengths in the far-UV. No obvious improvement is observed in the calculated spectra of regular β-sheet proteins. Our high-level ab initio calculations of the vibronic structure of the πnbπ* transition in NMA have provided some further insight into the physical origins of the nature of protein CD spectra in the far-UV.

scholarly journals Laser-induced fluorescence of free diamondoid molecules

2015 ◽  
Vol 17 (6) ◽  
pp. 4739-4749 ◽  
Author(s):  
Robert Richter ◽  
Merle I. S. Röhr ◽  
Tobias Zimmermann ◽  
Jens Petersen ◽  
Christoph Heidrich ◽  
...  
Keyword(s):  
Gas Phase ◽  
Laser Induced Fluorescence ◽  
Vibrational Structure ◽  
Complex Nature

We report on the laser-induced fluorescence of diamondoids in the gas phase. The spectra show well defined vibrational structure, whose complex nature is assigned with the help of TDDFT computations.

Experimental Construction of Reduced Mathematical Models of Rotating Equipments in Operation

2003 ◽  
Author(s):  
D. E. Goncalves ◽  
J. D. Sanjuan ◽  
S. E. Di´az ◽  
M. Pacheco
Keyword(s):  
Mathematical Models ◽  
Excitation Frequency ◽  
Base Plate ◽  
Industrial Applications ◽  
Impact Excitation ◽  
Weight Functions ◽  
Approximation Technique ◽  
Force Coefficients ◽  
Excitation Techniques ◽  
The Individual

An experimental method is proposed to obtain simplified mathematical models of rotating equipment systems. The Instrumental Variable Filter (IVF) method is applied to estimate mass, damping and stiffness force coefficients within a frequency range, through experimental measurements. This method is based on the least squares approximation technique and it uses analytical weight functions to reduce the effect of noise in the measurements. The experimental data is obtained for different configurations of rotating equipments, which consist of rigid wheels, a flexible shaft supported by bushing bearings, an electrical motor, a base-plate, and a concrete foundation. Frequency response functions (FRF) were obtained by impact excitation techniques. In the tests, the unbalanced response measurements were compared with the ones predicted by the IVF model. The method allows the study of mass, damping and stiffness force coefficients as a function of excitation frequency. Linearities and non-linearities of phenomena are identified, and the method sums up all the individual components into a definition for the system. The tests were conducted by operating, or not, the motor, in order to evaluate the IVF method in both cases. The high correlation between the IVF (FRF, and unbalance responses) and the actual measurements of the FRF and unbalance responses, shows that the method generates useful mathematical models of dynamic systems, that can have industrial applications. Modal analysis methods were used to compare the natural frequencies and the damping ratios, obtained by dynamic coefficients estimation.

Instability of Mooring Cables in Presence of Ice-Load

2016 ◽  
Author(s):  
Ritwik Ghoshal ◽  
Anurag Yenduri ◽  
Aziz Ahmed ◽  
Zhuo Chen ◽  
Wenping Wang ◽  
...  
Keyword(s):  
Geometric Nonlinearity ◽  
Excitation Frequency ◽  
Pulse Load ◽  
Base Excitation ◽  
Ice Load ◽  
Out Of Plane ◽  
Mooring Cable ◽  
Support Excitation ◽  
The Stability ◽  
Plane Mode

Station keeping system for arctic floaters such as mooring cables requires an innovative engineering design coupled with a detailed investigation on its resistance against the impact loading. The ice-induced vibration, together with the wave and current actions, imposes a strong demand on the mooring cable design. However, in present industry practice, the mathematical models/software used in designing the mooring cables for offshore structures use linear strain theory. In this paper, an analytical modal based procedure for underwater submerged cable considering its geometric nonlinearity is presented. Introducing geometric nonlinearity into the modal procedure enables coupling between different modes, which is not included in the standard the linear analysis of integrated mooring system. In the present analysis, the second in-plane and first two out-of-plane modes are considered to highlight the effect of geometric nonlinearity near the 2:1 internal resonance phenomena of underwater mooring cables. The differential equation for cable is solved using a modal decomposition method considering second-order terms of the finite strain tensor. A simply supported boundary condition is assumed at both ends of the cable. A unidirectional wave loading is considered and thereby, the floater will have two translational motions, i.e., surge and heave. The floater motions will cause a support excitation at the pinned connection between the floater and mooring. This phenomenon is modelled as a base excitation at the top support point of the mooring cable. The support excitation frequency is chosen to be close to the natural frequency of the second in-plane mode. Therefore, the in-plane mode is excited directly. Ice load is applied at the support from an out-of-plane direction as a pulse load which may come from the ice impact and/or breaking. So, the out-of-plane mode is excited parametrically. It is observed that the out-of-plane mode responses show instability under certain base excitation amplitude, i.e., the responses due to the pulse load from the ice impact never decay. This instability in the responses may lead to the fatigue failure of the mooring cables. It is observed that this instability in the responses arises from the modal interaction between the different modes, i.e., autoparametric excitation, which the linear analysis is unable to capture. Numerous simulations are carried out to determine the stability boundary of different out-of-plane modes for various amplitude and excitation frequency. The stability boundaries are also determined using the harmonic balance method to verify the results obtained from the modal analysis. It can be concluded from this analysis that the nonlinear coupling terms play a significant role, close to the 2:1 resonance region which can lead to an unstable response of the mooring cables in the presence of ice loads.

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