Ž . Spectrochimica Acta Part B 55 2000 6573 Absorbance vs. time curves at high heating rates in electrothermal atomic absorption spectroscopy G. Torsi  , F.N. Rossi, D. Melucci, P. Reschiglian, C. Locatelli, D. Di Cintio Department of Chemistry ‘G. Ciamician’, Uni  ersity of Bologna, Via F. Selmi 2, I-40126 Bologna, Italy Received 15 April 1999; accepted 4 November 1999 Abstract The absorbance vs. time curves that can be obtained in electrothermal atomic absorption spectroscopy with special atomizers and high heating rates can show a very steep increase of the signal from the baseline at the beginning of the atomization step, followed by a more or less extended flat region and by an exponential decay. This type of curve can be mathematically described by simple equations if rather drastic assumptions are made, i.e. if the atom supply is a delta function, if the absorbing species are homogeneously distributed in a plane at the center of a container of constant cross-section, and if the atom removal occurs only by diffusion. In this paper, some experimental curves are presented which are in satisfactory agreement with the theoretical model, thus supporting the claim that, with our atomization system and power supply, the existence of the flat region is indeed justified. With a new atomizer, specifically designed, it is possible to measure the diffusion coefficient of atoms in a gas at high temperature. However, for accurate measurements, the model must be refined and better measurements of the temperature of the atomizer must be obtained.  2000 Elsevier Science B.V. All rights reserved. Keywords: Electrothermal atomic absorption spectroscopy; Spectroscopic constant 1. Introduction The accepted model for describing absorbance Ž . A vs. time curves in electrothermal atomic Ž . absorption spectroscopy ETAAS is a convolu-  Corresponding author. Fax: 39-051-209-9456. tion integral of a source and removal functions   1,2 given by: t ' Ž. Ž . Ž . Ž. Nt  St ' Rt  t ' d t ' 1 H 0 Ž.Ž . where Nt atom is the number of atoms pre- Ž. Ž. sent in the atomizer at time t s , St is the rate 0584-854700$ - see front matter  2000 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 5 8 4 - 8 5 4 7 99 00168-8