The Particle in a Box Redux: Improved Experimental Conditions for the Laser Synthesis of Linear Polyynes

Abstract

The one-dimensional, particle-in-a-box model is an integral part of most undergraduate physical chemistry courses. Linear polyynes can be synthesized and are found to serve as real-world examples of the particle-in-a-box model. An improved set of experimental conditions for the laser synthesis of linear polyynes has been determined. Specifically, a Nd:YAG laser operating at 532 nm and 20 mJ/pulse for 5 min can produce sufficient polyynes to be detected with a UV–vis spectrophotometer. Students can use the experimental wavelength and the eigenvalue expression for the particle in a box to calculate the length of the box and compare it to the length of the molecule with good results. The lower laser energy used here is important because it enables a less costly laser to be used for the experiment, which will enable more instructors to incorporate the experiment into their curriculum.