Second harmonic generation spectroscopy interface

MOLECULAR RECOGNITION AT L/L INTERFACES AS STUDIED BY SECOND HARMONIC GENERATION SPECTROSCOPY... 

H. Wang, E. Borguet, and K. B. Eisenthal, The polarity of liquid interfaces by second harmonic generation spectroscopy, J. Phys. Chem. 101 (1997) 713. 

T. Uchida, A. Yamaguchi, T. Ina, and N. Teramae, /. Phys. Chem. B, 104, 12091 (2000). Observation of Molecular Association at Liquid/Liquid and Solid/Liquid Interfaces by Second Harmonic Generation Spectroscopy. 

Petraiii-Maiiow T, Wong T M, Byers J D, Yee H i and Hicks J M 1993 Circuiar dichroism spectroscopy at interfaces—a surface second harmonic-generation study J. Phys. Chem. 97 1383-8... 

Hirose, Y, Yui, H. and Sawada, T. (2005) Second harmonic generation-based coherent vibrational spectroscopy for a liquid interface under the nonresonant pump condition. J. Phys. Chem. B, 109, 13063-13066. 

In recent years,3 4 however, there has been renewed interest in the study of the electrode/solution interface due in part to the development of new spectroscopic techniques such as surface-enhanced Raman spectroscopy,5-7 electrochemically modulated infrared reflectance spectroscopy and related techniques,8,9 second-harmonic generation,10-12 and others which give information about the identity and orientation of molecular species in the interfacial... 

Nonlinear optical spectroscopies such as second harmonic generation (SHG) and sum frequency generation (SFG) are finding increasing use in probing species at interfaces (e.g., Eisenthal, 1996). For example, SHG was used by Donaldson et al. (1995) to detect a surface-bound S02 species, and SFG has been applied to elucidate the structure of dimethyl sulfoxide at liquid interfaces (Allen et al., 1999). These techiques are... 

As discussed in Chapter 8, enhanced reactions of S02 at the interface have also been observed (Jayne et al., 1990). Surface second harmonic generation (SHG) experiments (Donaldson et al., 1995) subsequently identified a unique adsorbed S02 species at the air-water interface that may be involved in this enhanced reaction. Such SHG work on the uptake and reaction of N02 on water would clearly also be of value in understanding the kinetic anomalies. In addition, the use of sum frequency generation (SFG) spectroscopy, which in effect allows one to obtain the infrared spectrum of species present at interfaces, may shed some light on such reactions. 

Refs. [i] Hoke R (2008) Surface and interface analysis an electrochemists toolbox. Springer, Berlin [ii] Tadjeddine A, Peremans A (1998) Non-linear optical spectroscopy of the electrochemical interface. In Clark RJH, Hester RE (eds) Advances in spectroscopy (spectroscopy for surface science), vol. 26. Wiley, Chichester, p 159 [iii] Shen YR (1990) In Gutierrez C, Melendres C (eds) Spectroscopic and diffraction techniques in interfacial electrochemistry (NATO ASI series C, vol. 320). Kluwer, Dordrecht, p 281 [iv] Shen YR (1986) Applications of optical second-harmonic generation to surface science. In Hall RB, Ellis AB (eds) Chemistry and structure at interfaces. VCH, Deerfield Beach, p 151 [v] Williams CT, Beattie DA (2002) SurfSci 500 545... 

Vibrational sum-frequency spectroscopy (VSFS) is a second-order non-linear optical technique that can directly measure the vibrational spectrum of molecules at an interface. Under the dipole approximation, this second-order non-linear optical technique is uniquely suited to the study of surfaces because it is forbidden in media possessing inversion symmetry. At the interface between two centrosymmetric media there is no inversion centre and sum-frequency generation is allowed. Thus the asynunetric nature of the interface allows a selectivity for interfacial properties at a molecular level that is not inherent in other, linear, surface vibrational spectroscopies such as infrared or Raman spectroscopy. VSFS is related to the more common but optically simpler second harmonic generation process in which both beams are of the same fixed frequency and is also surface-specific. 

J.C. Conboy, Investigation of Immiscible Uquid/Liquid Interfaces with Second Harmonic Generation and Sum-Frequency Vibratiorml Spectroscopy, University of Oregon, Eugene, 1996. 

Second harmonic generation has been recognized as a powerful probe to study the electronic states at surfaces and interfaces [16]. Under the electric dipole approximation, second-order nonlinear processes are forbidden in centrosymmetric systems. This principle makes the phenomena surface-specific in many cases. Indeed, the capability of SHG spectroscopy to explore surface electronic states has been demonstrated on various systems, dye molecules at solid/liquid interfaces [17], organic molecules at liquid/air interfaces [18], semiconductor surface states [19], organic molecules at metal surfaces [20], and so on. 

Sections 2 and 3 are in part based on a recent review article by Fischer and Hache [4]. The article gives an overview of chiral nonlinear optical spectroscopies in solution and at interfaces, and includes a discussion of second-harmonic generation from chiral surfaces [4]. 

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