Time-Resolved Second Harmonic Generation

Castro A, Sitzmann E V, Zhang D and Eisenthal K B 1991 Rotational relaxation at the air-water interface by time-resolved second-harmonic generation J. Phys. Chem. 95 6752-3... 

In addition to the fourth-order response field Tfourth, the probe light generates two SH fields of the same frequency 211, the pump-free SH field Eq(2 Q), and the pump-induced non-modulated SH field non(td> 211). The ground-state population is reduced by the pump irradiation and the SH field is thereby weakened. The latter term non(td, 211) is a virtual electric field to represent the weakened SH field. Time-resolved second harmonic generation (TRSHG) has been applied to observe E on (td, 211) with a picosecond time resolution [20-25]. The fourth-order field interferes with the two SH fields to be detected in a heterodyned form. 

Fuyukui, M., Watanabe, K. and Matsumoto, Y. (2006) Coherent surface phonon dynamics at K-coverd Pt(lll) surface investigated by time-resolved second harmonic generation. Phys. Rev. B, 74, 195412. 

Pozniak B, Mo YB, Stefan IC, Mantey K, Hartmaim M, Scherson DA. 2001. In situ time-resolved second-harmonic generation from Pt(lll) microfacetted single-crystal platinum microspheres. J Phys Chem B 105 7874-7877. 

As discussed in Section II.A, Eisenthal and coworkers have studied the related problem of isomerization at liquid-solid interfaces. They used time-resolved second harmonic generation to investigate the barrierless photoisomerization of malachite green at the silica-aqueous interface using femtosecond time-resolved second harmonic generation [26]. They found that the photoisomerization reaction proceeded but was an order of magnitude slower at the water-silica interface than in bulk solution. 

Teramobile, 112 Thomson scattering, 168, 179 Three-level system, 11 Three-step model, 65 Time-resolved second harmonic generation, 29 TOF spectroscopy, 5 Transient depletion field screening (TDFS), 28... 

Time-Resolved Second Harmonic Generation 19.2.2.1 Principles and Brief History... 

Chang Y. M., Xu L. and Tom H. W. K. (1999), Observation of local-interfacial optical phonons at buried interfaces using time-resolved second-harmonic generation , Phys. Rev. B 59, 12220-12223. 

A. Castro, E. V. Sitzmann, D. Zhang, and K. B. Eisenthal,/. PIrys. Chem., 95, 6752 (1991). Rotational Relaxation at the Air/Water Interface by Time-Resolved Second Harmonic Generation. 

R. Antoine, A. A. Tamburello-Luca, P. Hebert, P. F. Brevet, and H. H. Girault, Chem. Phys. Lett., 288, 138 (1998). Picosecond Dynamics of Eosin B at the Air/Water Interface by Time-Resolved Second Harmonic Generation Orientational Randomization and Rotational... 

FIGURE 8 (a) Time-resolved second-harmonic generation spectroscopy reveals the generation of coherent phonon modes in native oxide covered GaAs (100) crystal, (b) Left inset shows the oscillatory part of the time domain data, (c) Right inset shows the Fourier power spectrum of the oscillatory part. 

Lantz J M and Corn R M 1994 Time-resolved optical second harmonic generation measurements of picosecond band flattening processes at single crystal TiO, electrodes J. Phys. Chem. 98 9387-90... 

Meech, S. R. and Yoshihara, K. (1990) Time-resolved surface second harmonic generation a test of the method and... 

Optical detection offers the most conventional technique to time-resolve the coherent phonons. It includes four-wave mixing [8], transient reflectivity [9,10] and transmission [7] measurements, as well as second harmonic generation (SHG) [15,32]. Coherent nuclear displacement Q induces a change in the optical properties (e.g., reflectivity R) of the crystal through the refractive index n and the susceptibility y,... 

The same equipment, which is used for time-resolved Ivuninescence application is suitable for other laser-based spectroscopies. Thus several spectroscopic methods may be applied simultaneously. The most important techniques, which may be used together with time-resolved luminescence, are laser-induced breakdown spectroscopy, Raman spectroscopy and Second Harmonics Generation spectroscopy. 

The possibilities of time-resolved laser based spectroscopies have been demonstrated, combining such techniques as luminescence, Raman, breakdown and second-harmonic generation. Radiometric sorting of minerals using LIBS was patented and apparatus for evaluation of phosphate rocks with elevated dolomite content has been developed and constructed. 

The Applications of Laser-induced Time-resolved Spectroscopic Techniques chapter starts with a short description of laser-induced spectroscopies, which may be used in combination with laser-induced luminescence, namely Breakdown, Raman and Second Harmonic Generation. The chapter contains several examples of the application of laser-based spectroscopies in remote sensing and radiometric sorting of minerals. The proljlem of minerals as geomaterials for radioactive waste storage is also considered. 

Time-resolved fluorescence was used to detect rhodamine 6G (R6G), sulfor-hodamine 101 (SR101), and rhodamine B (RB). A Ti-sapphire laser (800 nm, 50 fs) was used, but the excitation wavelength has been converted to 400 nm (for R6G) or 532 nm (for SR 101 or RB) by an optical parametric amplifier or by second harmonic generation [676], In another report, fluorescence burst detection was used for detection of single chromophore molecules [677]. 

Figure 2 Schematic diagram of the time-resolved IR spectrometer. CLS, cavity length stabilizer SHG, second harmonic generator IS, intensity stabilizer BPS, beam pointing stabilizer CS, coherent seeder PR, polarization rotator.

Besides improving classical electrochemical methods, newly employed techniques such as second harmonic-generation and time-resolved fluorometry, with either control of the potential drop across the interface or fluctuation analysis, are promising in this respect. Also indispensable are further advances in molecular dynamics and statistical-mechanical treatments of structure and charge transfer at the ITIES. 

Finally, forward ISRS excitation can be followed by measurement of time-dependent absorption or Raman spectra, second harmonic generation efficiency, or any other optical property that may be affected by vibrational distortion. Preliminary time-resolved absorption spectroscopy of nonequilibrium, vibrationally distorted species is discussed further in the next section [46]. 

Chang, Y.M., Xu, L. and Tom, H.W.K. (1997) Observation of coherent surface optical phonon oscillations by time-resolved surface second-harmonic generation. Phys. Rev. Lett., 78, 4649-4652. 

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