An impressive approach to identify explosives, dangerous mixtures of gases and substances accurately and in short acquisition times has been suggested and experimentally proved by the researchers of University of Michigan, Bachana Lomsadze and Steven Cundiff.
A laser-based spectroscopic method has been developed to identify hazardous chemicals and be used for such practical applications as fundamental science, chemical sensing, materials characterizations, hence, environmental protection, airport systems or even in battlefields. The method combines two spectrographic techniques aimed at simultaneously providing high resolution and accelerating the process of detection of potentially dangerous chemicals.
The first technique, known as multi-dimensional coherent spectroscopy (MDCS), is used to determine the structure of the gas molecules with the help of ultra short laser pulses contributing to read the specific types of gases by specific wavelength of light they absorb. However, this technique requires a significant amount of time as well as high performance supercomputers to utilize complex schemes, especially while analyzing gases in a mixture. For this reason, being inspired by the MDCS approach, the researches of University of Michigan decided to combine the multi-dimensional coherent spectroscopy technique (MDCS) with another method called dual comb spectroscopy (DCS). This emerging spectroscopic tool is used to exploit the frequencies of atoms and molecules and measure a sample’s spectral response quickly and without limitations of conventional spectrometers. Frequency combs generate a spectrum of equally spaced sharp lines with the help of which it is easier to efficiently analyze the qualities and characteristics of a collection of molecules.
This newly developed method of combination of multi-dimensional coherent spectroscopy (MDCS) with dual comb spectroscopy (DCS) was used by the UM researchers, Cundiff and Lomsafze, to analyze a vapor of rubidium atoms containing two rubidium isotopes. The combinations of two techniques enabled the researchers to resolve the spectral difference between the two isotopes. Whereas, the usage of only multi-dimensional coherent spectroscopy (MDCS), would have been too insufficient and would make it impossible to measure the difference between absorption lines for the two isotopes. The process required the energy levels to be coupled by each others, which was achieved by adding dual comb spectroscopy (DCS) technique.
The scientists have plans to also apply a third laser to make the subsequent test even more accurate and precise, which would give an opportunity to expand the number of possible-to-identify chemicals and accelerate the process of the identification so it could be used practically, too.