摘要:

Recent research has expanded the capabilities of four-wave mixing by providing it with component selectivity, site selectivity, and mode selectivity. The selectivity is achieved by taking advantage of the three resonance enhancements that occur in a four-wave mixing process. New spectral scanning strategies allow one to scan a single resonance while maintaining the other two resonances at constant values. The constant resonances can be used to select a specific component, a specific site within an inhomogeneously broadened envelope of a component, and/or a specific vibrational or vibronic mode of that site. The scanned resonance will then contain enhanced features corresponding to the particular component, site, and/or mode that was chosen by the constant resonances. These component and site selective capabilities of the four-wave mixing complement the single vibronic level fluorescence methods. The relative transition intensities from a specific component or site reflect the mode coupling between the vibrational and vibronic modes. Since the four-wave mixing is fully resonant in these experiments, saturation effects play a dominant role and cannot be ignored. This review presents a complete discussion of the theoretical and experimental factors that control the fully resonant four-wave mixing. It shows examples of the component selectivity and the line narrowing capabilities. It also provides examples of how mode selection can identify mode coupling through the relative intensities of different vibrational features.

ISSN:0144-235X    

DOI:10.1080/01442359109353262

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In this review we describe CO on NaCl(100) as a model system for the exploration of surface structure and vibrational energy flow patterns. The system has been studied by a wide variety of surface science techniques in recent years. Thermodynamic measurements reveal the surface bond strength and polarized infrared spectroscopy demonstrates that the CO axis is perpendicular to the (100) face. Infrared photometry provides the radiative rate of the vibrationally excited CO monolayer on NaCl(100). Temperature-dependent bandshape measurements contain information on the dephasing rate. Several experiments in which the monolayer is vibrationally excited by a laser yield the phonon relaxation rate and provide an upper limit on the photodesorption rate. Infrared fluorescence from the excited monolayer has been monitored. The bond strength measurements, structure determinations, infrared band profile studies and the mapping ofallthe vibrational relaxation channels of CO on NaCl(100) comprise an unusually complete catalogue of experimental results. These results are used to test theoretical models that calculate structure and bonding, spectroscopic bandshapes and relaxation rates—with mixed success. CO on NaCl(100) appears unique among surface systems in that it is accessible to a wide variety of experimental explorations. Some of the theoretical models seem quantitatively reasonable but others, which may be qualitatively correct, need further development.

ISSN:0144-235X    

DOI:10.1080/01442359109353263

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0144-235X    

DOI:10.1080/01442359109353264

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor