UCSD Researchers Unveil IRiSTM for Single-Molecule Vibrational Detection

Researchers at the University of California San Diego, led by Assistant Professor Shaowei Li, have developed a groundbreaking new technique: infrared-integrated scanning tunneling microscopy (IRiSTM). This innovative method enables the detection of vibrations from individual molecules, a capability that distinguishes it sharply from traditional infrared spectroscopy, which typically measures the collective vibrations of large groups of molecules.

Understanding Molecular Vibrations: The Role of Infrared Spectroscopy

Molecules possess characteristic vibrations, where their chemical bonds stretch, bend, and twist at specific rates within the infrared region of the electromagnetic spectrum. These distinct vibrational patterns act as unique "fingerprints," offering insights into a molecule's chemical structure and its nanoscale environment.

Traditional infrared spectroscopy functions by measuring how light excites these molecular vibrations. However, the signals produced by individual molecules are very faint.

This has limited conventional infrared spectroscopy to detecting the combined vibrations of millions or billions of molecules simultaneously.

IRiSTM: A Novel Integration for Unprecedented Detail

The newly developed IRiSTM technique directly addresses this long-standing limitation. It achieves this by integrating infrared excitation with scanning tunneling microscopy (STM).

Scanning tunneling microscopy is a method utilized for imaging individual atoms and molecules by measuring the quantum tunneling of electrons between a sharp metal tip and a surface. This powerful combination allows researchers to observe how vibrational energy couples to molecular motion at a fundamental level.

Paving the Way for Future Chemical Control

Assistant Professor of Chemistry Shaowei Li highlighted the profound scientific implications of this innovation.

"This development contributes to the scientific objective of controlling chemical reactions through the precise deposition of energy into single bonds, a long-held ambition for chemists."