Twisted laser light can tell mirror-image molecules apart

Researchers at the Tata Institute of Fundamental Research have developed a method to identify mirror-image molecules using twisted laser light. Many molecules exist in two forms that are identical in composition but opposite in structure, similar to a left and right hand. These variations are critical in pharmaceuticals, where one version might provide a cure while the other causes harm.

Traditionally, separating and identifying these molecules requires complex equipment and precise measurements. This new approach uses laser pulses that possess both spin and a specific twist as they travel. When these beams hit chiral molecules, the interaction depends on the alignment between the light's twist and the molecule's handedness.

The team tested this technique on R- and S-Camphor gas samples. The laser pulses fractured the molecules, and a mass spectrometer measured the resulting ions. By analyzing the frequency and nature of the fragments, the researchers accurately distinguished between the two forms. This direct detection method provides higher sensitivity than existing optical systems.

This development removes the need for angular measurements or complex alignment setups. By focusing on ion signals, the team achieved a clearer reading of molecular identity. This simplicity holds potential for high-precision applications in chemistry and medicine where detecting the correct molecular shape is a core requirement for safety and performance.