Depth-resolved cathodoluminescence spectroscopy of silicon supersaturated with sulfur Appl. Phys. Lett. 102, 031909 (2013) Effect of plasma N2 and thermal NH3 nitridation in HfO2 for ultrathin equivalent oxide thickness J. Appl. Phys. 113, 044103 (2013) Atomic-scale characterization of germanium isotopic multilayers by atom probe tomography J. Appl. Phys. 113, 026101 (2013) Monitoring metal contamination of silicon by multiwavelength room temperature photoluminescence spectroscopy AIP Advances 2, 042164 (2012) Annealing studies of heteroepitaxial InSbN on GaAs grown by molecular beam epitaxy for long-wavelength infrared detectors J. Appl. Phys. 112, 083107 (2012) Additional information on Rev. Sci. Instrum. Trace gas detection of small molecules has been performed with cavity ring down (CRD) absorption spectroscopy in the near UV part of the spectrum. The absolute concentration of the OH radical present in trace amounts in heated plain air due to thermal dissociation of H 2 0 has been calibrated as a function of temperature in the 720-1125 0 C range. Detection of NH 3 at the 10 ppb level is demonstrated in calibrated NH 3 /air flows. Detection of the background Hg concentration in plain air is performed with a current detection limit below 1 ppt. The effect of the laser linewidth in relation to the width of the absorption line is discussed in detail. Basic considerations regarding the use of CRD for trace gas detection are given and it is concluded that CRD spectroscopy holds great promise for sensitive L(sub)-ppbl and fast (kHz) detection of many small molecules.

In a cavity ring down experiment the multi-mode structure of a short resonant cavity has been explicitly manipulated to allow a high spectral resolution, which is advantageous for the overall detection sensitivity as well. Coherent cavity ring down spectroscopy is performed around 298 nm on OH in a flame.

We report two complementary experimental investigations of the absorption spectrum of molecular oxygen between 243 and 258 nm. In the first experiment, excitation of O2 is inferred by detecting oxygen atoms resulting from chemical reaction. In the second experiment, absorption by O2 is observed directly by cavity ring-down spectroscopy. Absorption strengths for the Herzberg I [Formula: see text], Herzberg II [Formula: see text], and Herzberg III [Formula: see text] band systems are modeled with the DIATOM spectral simulation computer program using the best available branch intensity formulas. Absolute oscillator strengths are derived for all three systems and compared with values in the literature.

Doubly-resonant excitation/vibrational autoionization is used to accurately determine the ionization potential ͑IP͒ of the highly symmetric caged amine 1,4 diazabicyclo͓2,2,2͔octane ͑DABCO͒. The IP of DABCO excited with one quantum of the 24 (eЈ) vibration lies at ͑59 048.62Ϯ0.03͒ cm Ϫ1 , based on fitting 56 components of the np xy Rydberg series ͑␦ϭ0.406Ϯ0.002͒ to the Rydberg formula. Rydberg state transition energies and linewidths are determined using standard calibration and linefitting techniques. The IP determined from Rydberg state extrapolation is compared with that determined by mass analyzed threshold ionization ͑MATI͒. Effects of static electric fields on MATI signals measured for the high Rydberg states are discussed.

Laser-desorption jet-cooling has been applied in combination with mass-selective gas-phase spectroscopic techniques to study the structure and low-frequency vibrations of diphenylamine ͑DPA͒. Two-color ͑1ϩ1Ј͒ resonance-enhanced multiphoton ionization has been used to measure the vibrationally resolved excitation spectrum of the S 1 ←S 0 transition in the 305-309 nm region. Ion-dip measurements have been performed to determine the vibrational structure in the electronic ground state. The electronic spectra of DPA are dominated by long progressions in low-frequency vibrations involving the motion of the phenyl rings as a whole. For the interpretation of the experimental data ab initio calculations have been performed at the Hartree-Fock level for the S 0 -state and using single-excitation configuration interaction for the S 1 -state. The DPA molecule is found to change from a pyramidal geometry around the N-atom with unequal torsional angles of the phenyl groups in the S 0 -state to a planar geometry with equal torsional angles in the S 1 -state. The two most prominent vibrational motions are the in-phase wagging and the in-phase torsion of the phenyl rings. In addition, the resonance-enhanced multiphoton ionization spectra of the S 1 ←S 0 transition in the DPA-Ar, DPA-Kr, and DPA-Xe van der Waals complexes have been measured. From these spectra it is inferred that there is a coupling between the van der Waals modes and the low-frequency intra-molecular modes of DPA.