Nanosecond Laser Induced Transient Absorption Flash Photolysis Experiment for Undergraduate Physical Chemistry

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 15 (2010) pp 365-369

Nanosecond Laser Induced Transient Absorption Flash Photolysis Experiment for Undergraduate Physical Chemistry

Rolando Oyola*^,† and Rafael Arce^‡

^†Department of Chemistry, University of Puerto Rico-Humacao, Humacao, PR 00791;rolando.oyola@upr.edu; ^‡Department of Chemistry, University of Puerto Rico- Río Piedras, San Juan, PR 00936
Received February 19, 2009. Accepted April 9, 2010.

Published: 1 October 2010

Abstract. Research laboratories commonly perform studies of fast chemical reactions with lasers using fast and ultrafast spectroscopy. However, students at the level of undergraduate physical chemistry laboratory course rarely experience with fast spectroscopy techniques. Therefore, the objective of this laboratory experience is to introduce this student population to fast spectroscopy techniques by using a modular nanosecond laser induced transient absorption spectro-kinetic photometer (NLTRAS) in a Physical Chemistry laboratory course. The experimental setup proposed illustrates fundamental principles and instrumentation of fast spectroscopy and transient intermediates characterization, transient kinetics, and electronic spectroscopy appropriate for undergraduate physical chemistry level. The advantage of using the NLTRAS to generate the transient absorption spectra to study the kinetics of reactive intermediates is demonstrated by the laser induced triplet-triplet transient absorption spectrum measurements of thioxanthone in acetonitrile and of thiomethylpromazine in water. These molecules are chosen because they have a high intersystem crossing quantum yield (Φ_T>0.6) necessary for an adequate signal to noise ratio. In addition, alternative experiments with various learning objectives are recommended. Fundamental knowledge on spectroscopic techniques like NLRTAS will be an asset to those students pursing graduate studies and also for those that decide a career in industry.

Key Words: Laboratories and Demonstrations; physical chemistry; kinetics; spectroscopy

(*) Corresponding author. (E-mail: rolando.oyola@upr.edu)

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Supporting Materials:

The Supporting Material includes information for the different instrumentation components or parts. In addition, we include possible substitution components or parts that can be used (120 KB)