THE REFRACTIVE-INDEX OF AS-4 VAPOR BETWEEN 820-K AND 870-K STUDIED BYDISPERSIVE FOURIER-TRANSFORM SPECTROSCOPY IN THE VISIBLE (DFTS-VIS)

The density and wavenumber dependence of the refractivity [n(sigma, rh o, T) - 1] of As-4 in the gas phase has been determined by dispersive Fourier transform spectroscopy in the visible (DFTS-VIS, white-light i nterferometry). At a temperature T of 870 K (n - 1) can be described v ia (n - 1) = 3.3979 x 10(9) x rho/(5.18083 x 10(13) - sigma(2)), where rho is the amount-of-substance density given in mol m(-3) and sigma t he wavenumber of the measuring light in m(-1). The uncertainty in the refractivity is Delta(n - 1) approximate to +/- 1.2 x 1.0(-6). The ran ge of validity and the limitations of this relationship are discussed in detail.