Laserspectroscopy for Astrochemistry and the Earth’s Atmosphere

Lasers can be used in a wide variety of applications and LaserLAB has a long tradition of applied spectroscopic studies, notably also in laser isotope separation. Currently we are involved in applied spectroscopic studies, which relate to astrochemistry and the physics of light scattering in the atmosphere.

1) In the new NWO Astrochemistry program 2010 we investigate the photo-dissociation properties of small molecules, such as CO and N2. In particular the photodissociation of carbon monoxide in interstellar space, under the influence of the hard radiation from star-forming regions, is the driving force for the gas-phase chemistry in these environments. The LaserLAB extreme ultraviolet laser will be used for measuring predissociation rates of the various CxOy isotopomers. In addition we investigate the absorption spectra of unsaturated carbon chain molecules, which are known to exist in interstellar space. For this we use the technique of “cavity ring-down” absorption spectroscopy in conjunction with plasma jet discharges, in which these reactive species are produced.

2) In connection with the European Space Agency we investigate the light scattering properties of the Earth atmosphere. This is related to the planned ADM-Aeolus mission (Aeolus for the Greek God of the winds) with the objective to record the global wind profile by a satellite-based laser wind-lidar. The physical principle employs the Doppler effect; form the shifts in the lidar signal the wind velocity is extracted. However, in these studies it must be taken into account that the light scattering is not purely Gaussian, but at higher pressures Rayleigh-Brillouin profiles are observed, with characteristic side feature associated with acoustic waves. These effects are investigated in detail in our laboratory.

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Top: The plasma discharge jet in which carbon chain molecules arecreated and detected by CRD; Bottom: A Rayleigh-Brillouin profile of 90 degrees light scattering from a nitrogen atmosphere (at 3 Bar pressure to exaggerate the Brillouin phenomenon).

Contact: Wim Ubachs, email: wimu@nat.vu.nl, Harold Linnartz, and Ilse Aben.

Physics of light and matter