First operation of a sapphire-based Cerenkov free electron laser is reported. It is a tunable source of coherent millimeter and submillimeter radiation. The phase velocity of light in sapphire is about one-tenth of that in free space so that Cerenkov radiation is obtained at modest electron beam energies. In addition to its role as a Cerenkov coupler, the sapphire forms a high Q resonator obviating external mirrors. The spontaneous Cerenkov emission is well-confined by this resonator and can build to watts of power. Measured tuning and threshold currents are presented and compared with the predictions of free electron laser theory.

We report proton Zeeman relaxation rates in solid 1,4-di-isopropylbenzene (DIB) and in 1,3,5-tri-isopropylbenzene (TIB) at Larmor frequencies of 8.5 and 53 MHz. The temperature ranged from 110 to 300 K for DIB and from 85 to 240 K for TIB. In DIB the free induction decay contains both a liquid-like and a solid-like component at higher temperatures, and the solid-like component relaxes non-exponentially. In TIB the free induction decay is typical of molecular solids with reorienting methyl groups and the relaxation is always exponential. The model used to fit the temperature and frequency dependence of the Zeeman relaxation rates R in both moiecules suggests the occurrence of methyl reorientation only in the vicinity of and at temperatures below the observed maximum in R. Isopropyl reorientation does not occur except perhaps at the highest temperatures in TIB, where an additional motion begins to dominate the relaxation. These results are compared with the t-butyl analogues of these molecules in which the methyl and the t-butyl groups reorient at the same rate.

We have measured proton Zeeman relaxation rates R in the 2,4-and 2,5-isomers of di-tertbutylhydroxybenzene (DTHB) in the solid state. R was measured as a function of temperature T at proton Larmor frequencies of (j)/21T = 8.50,22.5, and 53.0 MHz. The Tranges were from 78 K to just below the melting points of 2,4-and 2,5-DTHB, 385 and 323 K, respectively. The 2,5-DTHB R vs T and (j) can be interpreted qualitatively in terms of three Bloembergen-PurcellPound (BPP) spectral densities, one for each of the three types of rotors in the molecule. The quantitative agreement is poor but a good fit is obtained using either a Davidson-Cole (DC) or Frolich spectral density, still preserving the three rotor types. The implications of this are discussed. The BPP and DC spectral densities fail completely in interpreting R vs T and (j) for 2,4-DTHBwhereas good quantitative fits are obtained using a Frolich spectral density. The distributions of activation energies characterizing the three rotor types are so wide for the Frolich spectral density fit of the 2,4-DTHB data that the individual rotor types lose their identity.

A.M. Albano et al. Phys. Rev. B 30, 2334 (1984 We investigate proton spin-lattice relaxation in two powdered organic molecular sohds with reorienting methyl (CH3) and tert-butyl [C(CH3)3] groups: 3,5-di-tert-butylphenol (DTBP) and 1,3,5-tri-tert-butylbenzene (TTBZ). The temperature and Larmor frequency dependence of the relaxation rate is considerably more complicated than would be expected on the basis of random reorientations of the CH3 and C(CH3)3 groups. The spectral densities describing the relaxation are broader, and show more structure, than those customarily used to interpret relaxation data. Assuming that the spectral densities may be expressed as linear superpositions of Lorentzians, we are able to obtain a single, nonexponential correlation function which leads to satisfactory fits of the data. Assuming also the validity of the Arrhenius relation,~=~"exp(E/kT), with a constant w", we find that the barriers to rotation for the CH3 and C(CH3)3 groups may be characterized by a distribution of activation energies consisting of a wide background and one (DTBP) or two (TTBZ) 5 functions.

This paper presents the results of patterned and unpatterned EUV mask inspections. We will show inspection results related to EUV patterned mask design factors that affect inspection tool sensitivity, in particular, EUV absorber material reflectivity, and EUV buffer layer thickness. We have used a DUV (257nm) inspection system to inspect patterned reticles, and have achieved defect size sensitivities on patterned reticles of approximately 80 nm. We have inspected EUV substrates and blanks with a UV (364nm) tool with a 90nm to a 120 nm PSL sensitivity, respectively, and found that defect density varies markedly, by factors of 10 and more, from sample to sample. We are using this information in an ongoing effort to reduce defect densities in substrates and blanks to the low levels that will be needed for EUV lithography. While DUV tools will likely meet the patterned inspection requirements of the 70 nm node in terms of reticle defect sensitivity, wavelengths shorter than 200 nm will be required to meet the 50 nm node requirements. This research was sponsored in part by NIST-ATP under KLA-Tencor Cooperative Agreement #70NANB8H44024.