Thermal treatment of a Mo/Si multilayer stack enhances its reflectivity in the soft x-ray region. The multilayer x-ray mirrors are fabricated by electron beam evaporation in ultrahigh vacuum. In situ measurement of the reflectivity during the deposition allows thickness control and an observation of changes in quality of the boundaries. By heating the substrates during deposition we obtain a smoothing of the interfaces. This leads to x-ray mirrors with peak reflectivity around 50% for normal incident radiation of wavelengths between 130 and 140 Å.

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This paper presents and discusses the adsorption of 0 2 and NO at Ni(IO0). The adsorption of 0 2 at Ni(100) is found to occur in four phases as indicated by LEED (p(2 x 2), c(2 x 2), c(2 x 2/~/3), NiO) and AES, whereas in the work function changes, only three dominant phases are evident. In the case of NO we found purely molecular adsorption at temperatures below 170 K in a disordered phase. At room temperature, molecular as well as dissociative adsorption (LEED c(2 x 2)) occurs. NO is desorbed at 380 K, but the LEED pattern is still visible even at higher temperatures up to 800 K. The superstructure of NO at Ni(lO0) is a N-and O-superstructure. The measurement of A~o shows that the dipole moment and the polarizability of the adsorbed NO are markedly higher as compared to the data of the gas-phase molecule. No oxidation of the Ni(lO0) surface could be observed even at a very high (500 L) NO exposure.

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