Related Experiment Video
Updated: Jul 2, 2026

Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional π-conjugate Systems
Published on: February 10, 2020
Sample modulated Raman spectroscopy and frequency modulated visible light--resonance Raman spectrum of a
C Tzinis1, S K Bahl, P Davidson
1Department of Chemistry, Brown University, Providence, RI 02912, USA.
Abstract:
Methods for obtaining sample modulated Raman (SMR) spectra and frequency modulated visible light are described. The sample modulated Raman method is one in which the frequency of the Raman scattered light is modulated by the sample which is responding to an externally applied periodic stress. The Raman active modes of the sample which are due to the vibrational motion of those molecular-scale units that change in response to the external stress are modulated and appear in the frequency-locked phase sensitively detected Raman spectrum. Those modes due to units that do not respond significantly to the stress do not appear. In principle the SMR method permits determination of those molecular units of a complex substance that are responsible for the substance's response to an external stress. The Raman scattered light is frequency modulated, has the wave form nu=nu(0)-nu(i)-(deltanu) sin(2pi ft), where nu(0) is the incident monochromatic light, nu(i) is the vibrational frequency of the statically stressed material, and (deltanu) is the magnitude of the frequency shift caused by the maximum stress applied at the frequency f.
Related Concept Videos
Raman Spectroscopy: Overview
However, a small fraction of the scattered light exhibits a frequency shift due to the exchange of energy between the incident photons and the...
Raman Spectroscopy Instrumentation: Overview
The monochromatic laser source, typically using visible or near-infrared radiation, generates a highly focused beam of light. This light interacts with the molecules of the sample, scattering some of the light. Liquid and gaseous samples are usually tested in ordinary glass capillaries, while solids can be analyzed as powders packed in capillaries or as potassium...
IR and UV–Vis Spectroscopy of Carboxylic Acids
However, the stretching absorptions for the C=O bond vary depending on the structure of carboxylic acids. The C=O bond of the free carboxylic acids shows a higher stretching frequency, 1760 cm−1, while H-bonded carboxylic acids (dimers) exhibit stretching absorptions at a lower frequency, 1710 cm−1. The C=O bond of the...
UV–Vis Spectroscopy: Woodward–Fieser Rules

