Theory of Vibrational Circular Dichroism and Infrared Absorption:  Extension to Molecules with Low-Lying Excited Electronic States

2004 ◽  
Vol 108 (35) ◽  
pp. 7222-7231 ◽  
Author(s):  
Laurence A. Nafie
Keyword(s):  
Circular Dichroism ◽  
Infrared Absorption ◽  
Electronic States ◽  
Vibrational Circular Dichroism ◽  
Excited Electronic States ◽  
Circular Dichroïsm

Film Techniques for Vibrational Circular Dichroism Measurements

2005 ◽  
Vol 59 (5) ◽  
pp. 673-681 ◽  
Author(s):  
Ganesh Shanmugam ◽  
Prasad L. Polavarapu
Keyword(s):  
Experimental Data ◽  
Circular Dichroism ◽  
Infrared Absorption ◽  
Film Formation ◽  
Vibrational Circular Dichroism ◽  
Protein Films ◽  
Amorphous Films ◽  
Free Standing ◽  
Circular Dichroïsm ◽  
Film State

Vibrational circular dichroism (VCD) spectra in the 1800–900 cm−1 region have been measured recently for protein films and for carbohydrate films prepared from aqueous solutions. In addition to the advantages of avoiding the interference from strong infrared absorption of water at 1650 cm−1 and requiring a two-orders-of-magnitude-smaller amount of sample for film measurements (than those required for the same in water solutions), the VCD bands in film measurements are found to be the same as those in solution measurements and to be independent of film orientation. This latter observation indicated the possibility for routine VCD measurements in the film state. In this manuscript we report different film techniques for VCD measurements. These techniques include preparation of supported films, free-standing films, film-on-film, and facilitation of film formation for substances that otherwise do not form amorphous films. The experimental data for films prepared by each of these techniques are presented and the relative merits of these different methods are discussed.

Circular dichroism measurements in the VUV

1991 ◽  
Vol 56 (12) ◽  
pp. 3012-3024
Author(s):  
Aharon Gedanken
Keyword(s):  
Circular Dichroism ◽  
Absolute Configuration ◽  
Electronic States ◽  
Vibrational Structure ◽  
Excited Electronic States ◽  
Selection Rules ◽  
Absorption Studies ◽  
The Absolute ◽  
Circular Dichroïsm

The extension of circular dichroism measurements into the VUV region was motivated by the need to provide supplementary techniques to the absorption studies lacking rotational and vibrational structure. CD as one of these techniques is determined by selection rules which differ from those in absorption and thus enables the assignment of excited electronic states. Another application of VUVCD measurements is the use of correlation between the sign of the CD signal and the absolute configuration to formulate sector rules of chromophores absorbing only in the VUV. In this review we will present results obtained on our home-made instrument capable of measuring CD signal down to 150 nm. These applications of VUVCD will be demonstrated in systems such as the oxirane chromophore, the methylenecyclohexene chromophore and the amine chromophore. The role of singlet-triplet transitions and their contribution to CD and ORD will also be discussed.

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