Broadband ICOS

A new technique by LGR combines the ICOS detection scheme with the use of a spectrally broad light source where the output of the cavity is spectrally dispersed and recorded by a CCD. The output of the cavity is sent through a wavelength dispersing element (such as a monochromator), and then to a linear detector array. Using a broadband dye laser, we can produce tens of nanometers of injection bandwidth. The approach was first demonstrated using the weak oxygen b-X (1,0) band as a test absorption gas¹.

This paper (referenced below) focused upon the time domain analysis; however, as seen in the journal cover picture (shown below), the ICOS image is clearly burned into the false color spectrum. The time domain results are plotted below, where the broadband ICOS spectrum is also evident in the intensity (false color) spectrum superimposed upon the CRD results.

The combined time domain and broadband ICOS spectra of the weak oxygen b-x (1,0) band is clearly seen. The BB-ICOS spectrum can be recovered by doing a linear integration along a line at any constant height (the time axis in the Spectral Photography image).

Currently, LGR is working with Farid Salama at NASA Ames to develop a new BB-ICOS system to measure the spectra of PAH molecular ions formed in a molecular beam. This system has been designed in a collaboration between LGR and the Saykally Group at UC Berkeley that has pioneered the development of such molecular beam sources for use in Cavity Ringdown studies. LGR is currently preparing the results of these studies for publication and will present the results here soon.