Christopher S. Gudeman

Completing the iron period: double-resonance, fluorescence-dip Rydberg spectroscopy and ionization potentials of titanium, vanadium, iron, cobalt, and nickel

We have used the fluorescence-dip technique to obtain double-resonance spectra of transition-metal atoms produced in a rf glow-discharge sputtering machine. Rydberg spectra of the neutral elements Ti, V, Fe, Co, and Ni have been analyzed to yield ionization potentials accurate to 1 cm−1, completing the table of values for the iron period (K through Zn). The 63 737-cm−1 value obtained for Fe agrees with a recently reported result, and new ionization potentials for Ti, V, Co, and Ni are 55 073, 54 413, 63 565 and 61 619 cm−1, respectively. Quantum defects for nd and ns series were obtained. Series converging to some excited ion core levels do not show detectable s–d mixing, which would provide a direct ionization channel and lead to the asymmetric line shapes that are characteristic of autoionization. Fano q parameters were determined for states autoionizing without a change in core configuration. Resolved spectra of low-lying Rydberg states display a complicated level structure not observed in studies of alkali or rare-gas atoms.

Rotationally resolved dicopper (CU2) laser-induced fluorescence spectra

We have used an RF sputter source to produce gas‐phase copper dimer molecules for study with laser‐induced fluorescence spectroscopy. Rotationally resolved spectra of transitions from the electronic ground (X) state to the A, B, C, G, and J states have been obtained. Previous rotational analyses of the X, A, and B states are confirmed. Analysis of the X–C spectrum shows the C state to have Π(Ω=1) symmetry, and a bond length of 2.26 A. Its vibrational constants are refined slightly. The J state has a bond length of 2.15 A, and shows evidence of extensive perturbation. Emission lifetimes at the bandheads of its lowest two vibrational states are 80 ns. Franck–Condon factors for the X–C and X–J transitions have also been obtained. The new J state bond length supports conclusions drawn from a recently obtained photoelectron spectrum of Cu2: the cation ground state indeed corresponds to loss of a 4sσ electron, and the excited state is due to removal of a 3d electron. Bond strengths and distances in the various ...

The mechanism of ultraviolet bonding of perfluoropolyether lubricants (used in magnetic recording)

It has recently been reported that thin films of perfluoropolyethers can be bonded to a variety of substrates under illumination with 185-nm ultraviolet light. In the present work, the authors examine the mechanism through which the bonding of the perfluoropolyethers to the substrate takes place. The perfluoropolyethers undergo dissociative electron attachment caused by photoelectrons that are generated by the interaction of the ultraviolet light with the substrate. This dissociative electron attachment results in the formation of a negative ion and a radical. It is suggested that subsequent radical propagation and termination steps then cross-link the perfluoropolyether and bond it to the substrate. >

Glow‐discharge optical spectroscopy as a diagnostic of sputtered permalloy film composition and saturation magnetostriction

We show that the composition and saturation magnetostriction of sputtered permalloy films can be correlated with the relative intensities of iron and nickel atomic emissions from a 13.56‐MHz rf glow discharge. Wavelength‐resolved emission spectra as a function of discharge pressure were recorded while sputtering iron and permalloy targets. Intensities of some emission lines were highly correlated, so that their ratios were nearly independent of argon pressure. This occurred in spite of a ∼50‐fold change in the brightness of the glow over the pressure range studied, and suggested that the stoichiometry of the sputtering target and the sputtered permalloy film can each be assessed during the sputtering process. The selection of appropriate emission lines is discussed, along with considerations of the type of equilibrium distribution prevalent in a sputtering discharge. We used five sputtering targets with different Ni/Fe ratios to grow films. The films were analyzed in terms of composition, stress, and satu...

Radiofrequency sputter source for laser-induced fluorescence studies of transition metal atoms and dimers

Abstract We have developed a radiofrequency sputter source using a 13.56 MHz transmitter and operating in the pressure range 2–100 mTorr. Absorption, emission, and laser-induced fluorescence spectroscopies have been used to characterize the number densities and temperatures of metal atoms and molecules in the discharge. With an iron target, at a pressure of 100 mTorr, the ground-state iron atom density is 2 × 1012 cm−3, with a translational temperature below 800 K. We estimate a number density of copper dimers of 1010–1011 cm−3 when sputtering a copper target at this pressure, and find a rotational temperature of about 500 K. As an example of the sources utility, a rotationally resolved spectrum of the Cu2 C↔X transition is analyzed to yield the excited-state symmetry and rotational constants.

Spatially resolved measurement technique of magnetic anisotropy fields using the magneto‐optic Kerr effect

In this paper a novel method that permits spatially resolved measurements of the anisotropy field and easy axis direction is reported. The technique employs a Kerr based sensor that monitors the direction of magnetization φ of a magnetically soft thin film while an applied field is rotated in the plane of the film. The magnitude of the rotating field is set approximately to twice the anisotropy field (Hk), and thus the film remains saturated at all times and the domain wall artifacts reported previously are eliminated. φ and the direction of applied field β are then independently measured. We show that the amplitude and phase of sin(β−φ) are related to Hk and the easy axis orientation (EAO), respectively. The amplitude and phase information can be easily determined by first normalizing and then applying a fast Fourier transform to the digitally captured Kerr signal. Operationally, computer controlled translation stages are used to scan the sample under the Kerr laser beam, which is fixed with respect to t...