Set up of a Microbalance to Measure Very Low Masses

In the Laboratory of Experimental Astrophysics of the Universidad Politecnica de Valencia we make ices analogs to those that can be found in different astrophysical environments as, for example, interstellar medium and in many objects of our Solar System. We study several characteristics of these ices, like density integrated absorbance of its main absorption bands and refractive inde. In order to obtain the first, we need to measure the thickness (around 1 micrometer) and the mass (around 60 micrograms with relative error around 3%.). The first one is obtained by interferometry with lasers and the second using a quartz crystal microbalance (QCMB). It utilizes the piezoelectric qualities of quartz crystal. The application of an electric field to the gold coated quartz crystal causes a shear deformation (parallel to the gold surface). The crystal can reach the resonance if an alternating electric field is applied at a particular frequency that, for its part, depends on the mass deposited on it.