Related Experiment Video
Updated: Jun 27, 2026

Evanescent Field Based Photoacoustics: Optical Property Evaluation at Surfaces
Published on: July 26, 2016
[The influence of CO2 molecular relaxation dynamics on photoacoustic signal in near infrared (NIR) range]
Jin-song Li1, Kun Liu, Wei-jun Zhang
1Laboratory of Atmospheric Optics, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China.
Abstract:
Photoacoustic spectroscopy (PAS) based on tunable diode laser (TDLPAS) is a widely recognised method for its excellent performance in trace gas monitoring and spectral analysis. This spectral technique provides many advantages such as high selectivity and sensitivity, on-line, real time and contactless measurements in a compact experimental arrangement. In the present paper, a resonant PA spectrometer based on a low-power near infrared distributed feedback (DFB) diode laser and a home-made resonant PA cell operating on its first longitudinal mode is developed, and the PA system has the advantage of simple experimental setup, easy operation, and low-cost, room temperature operating, etc. By investigating the performances of the PA cell at first, a good agreement was achieved between experimental and theoretical results; we have systematically investigated the influence of molecular relaxation effect on the PA detection of CO2 molecule near 1.573 microm, and presented the relevant analysis in theory. The research result shows that the detection sensitivity of the system based on PAS technique can be effectively improved by using the molecular relaxation effect.
Related Concept Videos
IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration
According to Hooke's law, the vibrational frequency is directly proportional to the...
IR Spectroscopy: Molecular Vibration Overview
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
Infrared (IR) Spectroscopy: Overview
Different compounds display unique properties due to their...
¹³C NMR: ¹H–¹³C Decoupling
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
IR Absorption Frequency: Delocalization
In IR spectroscopy,...
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...

