Transient vibration

Figure 15.4 (a) Linear O-H stretching band of cyclic acetic acid dimers, (b) Transient vibrational absorption spectra measured for different pump-probe delays. The change of vibrational absorbance AA, for pump and probe pulses of parallel linear polarization is plotted as a function ofthe probe frequency. 

Dimer structures containing two O-H - -O (OH/OH dimer) or two O-D- -O (OD/OD dimer) hydrogen bonds were dissolved in CCI4 at concentrations between 0.2 and 0.8 M. Two-color pump-probe experiments with independently tunable pump and probe pulses were performed with a 100 fs time resolution. Approximately 1% of the dimers present in the sample volume were excited by the 1 pj pump pulse. After interaction with the sample, the probe pulses were spectrally dispersed to measure transient vibrational spectra with a spectral resolution of 6 cm 1. 

A similar study with substantially improved time resolution has been reported recently [8, 37, 38]. In such experiments, HBT was excited to the enol-Sj state by a 40 fs pulse at 350 nm, i.e., nearly resonant to the Sq-Sj transition. Transient vibrational spectra were measured with 100 fs mid-infrared probe pulses which were spectrally dispersed after interaction with the sample. Such spectra are displayed in Fig. 15.8 (b) for different delay times, together with the stationary vibrational spectrum in the enol ground state of HBT [Fig. 15.8 (c)j. In agreement with Ref [7], the spectra display a prominent new band around 1530 cm i with a spectral... 

Figure 15.8 (a) Molecular structures ofthe enol (left) and keto (right) tautomer of HBT. (b) Transient vibrational spectra of HBT after femtosecond excitation of the enol tautomer at 335 nm. The change in vibrational absorbance in mOD is plotted as a function of probe frequency for different time delays after electronic excitation. The spectra show the build-up of the carbonyl stretching band ofthe keto tautomer at 1535 cm. The absorbance changes at lower frequencies are due to skeletal modes, (c) Ground state... 

UV-Vis flash photolysis is the most widely used technique with which to follow fast photochemical reactions. However, although flash photolysis provides excellent kinetic information about excited states and reaction intermediates, UV-Vis spectra in solution are often broad and featureless and provide little structural information. Moreover, in experiments where several photoproducts are produced, overlapping of the broad absorption bands can make it very difficult to elucidate the mechanism. Transient vibrational spectroscopy provides more detailed structural information to probe photochemical reactions especially since Raman and IR bands of large molecules in solution are generally much narrower than UV-Vis bands. 

R. Lingle, Jr., X. Xu, S. Yu, H. Zhu, and J. B. Hopkins, J. Chem. Phys., 93, 5667 (1990). Ultrafast Investigation of Condensed Phase Chemical Reaction Dynamics Using Transient Vibrational Spectroscopy-Geminate Recombination, Vibrational Energy Relaxation, and Electronic Decay of the Iodine A Excited State. 

Transient Vibrational Spectroscopy for Identification of Jt-Electron Rotation... 

In a real mechanical system, the free vibration is always transient vibration, which dies out due to the positive viscous damping and the frictions. 

FIGURE 4.1.23 Transient vibration of a bimorph excited after a pseudo-step voltage applied, n is a time scale with a unit of half of the resonance period, that is, 2n = resonance period. 

Shock. Mechanical shock can be defined as a pulse, step, or transient vibration, wherein the excitation is nonperiodic. Shock is a sudderrly apphed force or increment of force, by a sudden change in the direction or magnitude of a velocity vector. With few exceptions, shocks are not easily transmitted to electronic equipment by relatively light mounting... 

The comprehensive vibration assessment programme against steady-state and transient vibration was performed at the Yonggwang Units 3 and 4. As a result, the structural integrity of the reactor internals against steady-state and transient vibration had been confirmed. 

Transient vibrational dynamics. Perturbation theory yields an intuitive picture of adsorbate relaxation the loss of a vibrational quantum and associated nodal structure in the nuclear wave function is coupled to an irreversible transfer of momentum to the metallic electrons (see Fig. 2). To obtain time-resolved information about the dynamical processes at work, it is nonetheless necessary to go beyond this simple model. In the past decades, classical molecular dynamics has been hugely successful at shedding light on the transient vibrational evolution in a variety of adsorbate-surface systems (see, e.g., ref. 54-56). The methods of choice for including non-adiabatic effects on the dynamics can be divided in two main families friction-lype... 

From a quantum mechanical perspective, the transient vibrational relaxation dynamics is often studied within a reduced density matrix formalism. The dissipative dynamics of the so-called open system is described by a Liouville von Neumann equation that includes implicitly the effects of the surroundings on the dynamics... 

Spanos PD, Solomos GP (1983) Markov approximation to transient vibration. J Eng Mech Div ASCE 109 1134-1150... 

Shinozuka M, Sato Y (1967) Simulation of nonstationary random process. J Eng Mech (ASCE) 93 11 0 Spanos P, Solomos GP (1983) Markov approximation to transient vibration. J Eng Mech (AS(2E) 109 1134—1150 Vamnarcke EH (1972) Properties of spectral moments with applications to random vibrations. J Eng Mech (ASCE) 98 425-446... 

Forced vibration (steady-state), and transient vibration... 

The reactor module will experience random, periodic, and transient vibrations mechanically transmitted from the launch vehicle, as well as acoustically induced random vibrations mechanically transmitted from adjacent Spaceship elements. (Ref 10- 2) These environments are typically described by a random vibration spectrum for components which are not directly excited by the acoustic environment. 

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