Phonon spectroscopy, .

Chang, Y.-M. (2003) Coherent phonon spectroscopy of GaP Schottky diode. Appl. Phys. Lett., 82, 1781-1783. 

With development of ultrashort pulsed lasers, coherently generated lattice dynamics was found, first as the periodic modulation in the transient grating signal from perylene in 1985 by De Silvestri and coworkers [1], Shortly later, similar modulation was observed in the reflectivity of Bi and Sb [2] and of GaAs [3], as well as in the transmissivity of YBCO [4] by different groups. Since then, the coherent optical phonon spectroscopy has been a simple and powerful tool to probe femtosecond lattice dynamics in a wide range of solid... 

Fainberg, B. D. and Huppert, D. (1999) Theoretical and experimental study of ultrafast solvation dynamics by transient four-phonon spectroscopy, in Jortner, J. and Bixon. (eds.), Advances in Chemical Physics 107, Part 1, John Wiley Sons. NY., pp 191-262. 

This paper presents studies of solid state polymerization aimed towards formulating a dynamic model of reactivity in the condensed phase. Phonon spectroscopy is successfully used to elucidate the mechanism of lattice control of the reaction. Novel concepts of phonon-assisted thermal and photochemical reactions are introduced, supported by experimental data. Non-linear laser spectroscopy is used to find the importance of biexcitonic processes in photopolymerization. Also, spectroscopic studies of reactions in Langmuir-Blodgett films and at gas-solid interface which produce ordered polymers are presented. 

To obtain information on the role of dynamics of molecular motions in the reactive systems, the approach of phonon spectroscopy is used. Phonons are low-frequency cooperative lattice vibrations of a solid and, therefore, probe the lattice interactions and dynamics directly. Phonons can be observed as optical transitions in the Raman spectra and in the electronic spectra (in the latter as a phonon side band). Some information regarding averaged librational and translational phonon motions can also be obtained from the rigid-motion analysis of the thermal parameters of x-ray diffraction studies. 

Phonon spectroscopy has been found to be a powerful method to Investigate the reaction dynamics In solid state. Also, non-llnear laser spectroscopic study has been used to probe the dynamics of photochemical reactions. Future directions are clearly a more quantitative and theoretical formulation of the Importance of energy state dynamics In determining reactivity In the condensed phase. Non-llnear spectroscopy as well as time-resolved X-ray crystallography using synchrotron radiation can be expected to provide valuable approaches for future development of a dynamic model of solid state polymerization. 

Han P Y, Cho G C and Zhang X C 1999 Mid-iR THz beam sensors expioration and application for phonon spectroscopy, uitrafast phenomena in semiconductors iii Proc. SPiE 3624 224-33... 

Laser induced phonon spectroscopy has been used to study the ultrasonic properties of nematic sidechain LCEs [47, 48], It has been shown that both the ultrasonic velocity and the attenuation show a strong anisotropy and it was concluded that the coupling between density changes and reorientation-al motion of the sidechains takes place on a time scale of 10" -10" s [47]. 

Ultrasonic experiments using laser induced phonon spectroscopy have been performed in a nematic liquid single crystal elastomer [48]. The experiments reveal a dispersion step for the speed of sound and a strong anisotropy for the acoustic attenuation constant in the investigated frequency range (100 MHz -1 GHz). These results are consistent with a description of LCEs using macroscopic dynamics [54-56] and reflect a coupling between elastic effects and the nematic order parameter as analyzed in detail previously [48]. 

Acoustic waves can be generated by optical pulses. Laser induced phonon spectroscopy is a technique applied to the study of molecular processes. In our case the 10-]um grating implies an acoustic period... 

Let the local functions Wj f r) = W<(r — q), (i = 1, 2,..., n ) be centered at point q of the direct lattice and span the space of the irrep / of the site-symmetry group Gq C G with matrices d > gq) and characters X H9q) 9q Gq) The nature of these functions depends on the physical problem under consideration. In the electron-band theory of crystals lF) (r — qA) are atomic functions of atom A. In phonon spectroscopy applications — qA) mean the components of atomic displacements of... 

Spin-polarized scanning tunneling spectroscopy (SPSTS) Phonon spectroscopy by inelastic electron tunneling (lET) Photoassisted tunneling spectroscopy (SFES) Tunneling-induced luminescence spectroscopy (TILS)... 

Taking as the only experimental parameter the CBC to CBB relation from phonon spectroscopy (53,204), the CBC, CBB and BDB concentration were calculated (Fig. 49). Subsequently the concentrations of B12 and BnC icosahedra (Fig. 50) immediately follow from the stoichiometry of the compound. The calculated BDB concentrations agree with the concentrations of B(3) vacancies determined by neutron diffraction. Compared with Fig. 26 (based on absolute oscillator strengths experimentally determined) the results in Fig. 49 and 50 (based on the quotient of oscillator strengths) show remarkable differences in the more boron-rich range only. The results in Figs. 49 and 50 are more reliable because in the quotient, systematic experimental error is largely eliminated (for details see (202)). 

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