Selection vibrational

Quack M 1991 Mode selective vibrational redistribution and unimolecular reactions during and after IR-laser excitation Mode Selective Chemistry ed J Jortner, R D Levine and B Pullman (Dordrecht Kluwer) pp 47-65... 

In the uracil dihydrate the harmonic NiH and N3H stretching modes are shifted by more than 200 cm [97JST323, 98JST307]. The influence of halogen substituents on selected vibrations has been investigated for 5-halogenouracils [98JST115]. 

Microscopy methods based on nonlinear optical phenomena that provide chemical information are a recent development. Infrared snm-frequency microscopy has been demonstrated for LB films of arachidic acid, allowing for surface-specific imaging of the lateral distribution of a selected vibrational mode, the asymmetric methyl stretch [60]. The method is sensitive to the snrface distribntion of the functional gronp as well as to lateral variations in the gronp environmental and conformation. Second-harmonic generation (SHG) microscopy has also been demonstrated for both spread monolayers and LB films of dye molecules [61,62]. The method images the molecular density and orientation field with optical resolution, and local qnantitative information can be extracted. 

Successful applications of fourth-order coherent Raman scattering are presented. Interface-selective detection of Raman-active vibrations is now definitely possible at buried interfaces. It can be recognized as a Raman spectroscopy with interface selectivity. Vibrational sum-frequency spectroscopy provides an interface-selective IR spectroscopy in which the vibrational coherence is created in the IR resonant transition. The two interface-selective methods are complementary, as has been experienced with Raman and IR spectroscopy in the bulk. 

Selected Vibrational Frequencies, Huang-Rhys Factors, and Electronic Energy Levels of the Involved States of RCs of Rb. sphaeroides... 

TABLE 2. Selected vibrational frequencies (cm ) of s-trans- 1,3-butadiene computed at several levels of calculation0... 

Table 12.3 Selected Vibrational Modes as Determined in MP2 Calculations for the [C4Cilm] + Cation in A A and GA Conformation...

Selected Vibrational Frequencies for Species Involving Oxygen Bonds... 

S. Masuda and S. A. Rice. Selective vibrational population transfer using combined STIRAP and counter-diabatic fields. J. Phys. Chem. C, (2014), DOI 10.1021/jp507923s. 

The detailed examination of the spectra of simple molecules is a direct source to determine the characteristic NIR frequencies for selected vibration modes. For qualitative and quantitative analyses there is the requirement to interpret as much as possible the NIR spectrum. Although interpretation of spectra in a manner analogous to MIR is not conceivable, attempts exist to define and categorize observed NIR frequencies. Examples of reported frequencies for aliphatic hydrocarbons are given in the following list ... 

The original theory of individual state-selective vibrational transitions induced by IR femtosecond/picosecond laser pulses has been developed by Paramonov and Savva et al. for single laser pulses [13] (see also Ref. 23) followed by more general extensions to series of IR femtosecond/picosecond laser pulses in Refs. 14 and 24. For illustration, let us consider two simple, one-dimensional model systems that are assumed to be decoupled from any... 

Figure 1. Morse potential V(q), vibrational levels Ev, and wave functions < (q) for the model OH (adapted from Ref. 14). The arrows indicate various selective vibrational transitions as well as above-threshold dissociations (ATDs) induced by IR femtosecond/picosecond laser pulses, as discussed in Sections III.A-III.D see Figs. 3-5. Horizontal bars on the arrows mark multiple photon energies ha of the laser pulses cf. Table 1. The resulting ATD spectrum is illustrated by the insert above threshold.

Extensions from the preceding ideal, isolated systems to others that are coupled to an environment are quite demanding and nontrivial [32] because the IR femtosecond/picosecond laser pulse has to achieve the selective vibrational transition (9) in competition against nonselective processes such as dissipation. For simulations, we employ the equation of motion for the reduced-density operator... 

Figure 3. Selective vibrational transitions OH(l>, = 0) - OH(ty = 5) and OH(u, = 5)->-OH(iy = 10) induced by two individual IR femtosecond/picosecond laser pulses. The electric fields c(i) and the population dynamics Pv(t) are shown in panels (a) and (b), respectively. Sequential combination of the two individual laser pulses yields the overall transition OH(u = 0) - OH(u = 5) - OH(u/ = 10) cf. Fig. 1 and Table I. For the isolated system, the population of the target state Pv= fo(t) is constant after the series of IR femtosecond/picosecond laser pulses, i > 1 ps.

The H2 molecule is a system for which quite recently it has been possible to measure in unprecedented detail state-selected vibrationally and rotation-ally resolved photoionization cross sections in the presence of autoionization [27-29]. The technique employed has been resonantly enhanced multiphoton ionization. The theoretical approach sketched above has been used to calculate these experiments from first principles [30], and it has thus been possible to give a purely theoretical account of a process involving a chemical transformation in a situation where a considerable number of bound levels is embedded in an ensemble of continua that are also coupled to one another. The agreement between experiment and theory is quite good, with regard to both the relative magnitudes of the partial cross sections and the spectral profiles, which are quite different depending on the final vibrational rotational state of the ion. 

Figure 29. Relative cross sections for collisional dissociation of CHjBr in selected vibrational-energy states as function of kinetic energy. Data were obtained by photoion photoelectron coincidence technique and were analyzed by assuming only backscattering in center of mass. Maxima of curves were normalized to same relative cross section.86b...

Molecular total energy is a sum of its kinetic (E ), potential (Ep), electronic (Select), vibrational (Evlhr), and rotational energy ( rot). Usually, the magnitude of these energies decreases in the following sequence Ekin > Ep > elect > I%lh, > EIot. 

Table 6 Selected vibration frequencies (in cm 1) observed in the argon matrix at 10 K and in the crystal state and calculated in the gas phase (B3LYP/6-31G ) of 1H- and 2H-tautomers of parent tetrazole <2001PCP3541 >...

A different perspective of the vibrational structure of the Sj electronic state is illustrated in Figure 2.13b. This is an OODR that was obtained by sequentially exciting CI2CS with two photons of different colors. In this experiment, a photon from the first laser (the pump photon) induces a Si <— So vibronic transition that is followed after a short time delay by a second S2 Si, probe photon that carries the excitation to the S2 state. The pump laser is advanced to the blue and interrogates the bands of the S2 <— So system while the probe laser is scanned at the same rate to the red such that the total energy matches a selected vibrational level of the S2 state. In this way, an excitation spectrum of the vibrational band structure of the S2 state is constructed by monitoring the fluorescence that originates from the S2 state. 

The basic theoretical framework for understanding the rates of these processes is Fermi s golden rule. The solute-solvent Hamiltonian is partitioned into three terms one for selected vibrational modes of the solute, including the vibrational mode that is initially excited, one for all other degrees of freedom (the bath), and one for the interaction between these two sets of variables. One then calculates rate constants for transitions between eigenstates of the first term, taking the interaction term to lowest order in perturbation theory. The rate constants are related to Fourier transforms of quantum time-correlation functions of bath variables. The most common... 

The vibrational energy levels of the B rio electronic state of I2 were studied by absorption spectroscopy in Exp. 39. In the present experiment, selected vibrational-rotational levels of this state will be populated using a pulsed laser. The fluorescence decay of these levels will be measured to determine the lifetime of excited iodine and to see the effect of fluorescence quenching caused by collisions with unexcited I2 molecules and with other molecules. In addition to giving experience with fast lifetime measurements, the experiment will illustrate a Stem-Volmer plot and the determination of quenching cross-sections for iodine. Student results for different quenching molecules will be pooled and the dependence of the cross sections on the molecular properties of the collision parmers will be compared with predictions of two simple models. 

Non-Resonant Excitation and Emission Detection on Selected Vibrational Satellites... 

The geometry and selected vibrational frequencies of CUTiCHa have been calculated using the LCGTO-Xa method. The methyl group is found essentially undistorted, thus providing no indication for an agostic interaction. 

Table II. Selected vibrational frequencies (in cm ) of the methyl group...

Figure 4. Selected vibrational modes of phenoxyl radical calculated by using the B3LYP/6-31G(d) method, including mode symmetries and both calculated(24) and experimentally measured frequencies.(i5-57)...

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