7 research outputs found

    Studies of ionic alkali halide excimer molecules excited by laser-produced plasmas

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    New ionic states of alkali halide molecules, which are isoelectronic to the neutral rare gas halide molecules, have been generated by direct photoionization using the soft x-ray flux from a laser-produced plasma. The fluorescence emission of three ionic excimer transitions has been observed at 185 nm for CsF, 208 nm for CsCl, and 130 nm for RbF. The emission wavelengths are in good agreement with those calculated using Rittner-type potentials. The vibrational structure in the emission spectrum of CsF has been calculated and excellent agreement with the experiment is found. A model for photoionization of these molecules has revealed that the vibrational population of the bound photoionized state is Boltzmann distributed if the neutral ground state has a thermal vibrational distribution. Molecular halogen transitions of Cl\sb2* at 258 nm and F\sb2* at 158 nm have been observed in CsCl and RbF, respectively, as a result of predissociation of the ionic states of these molecules. Rate constants for the molecular halogen formation and lifetimes for the precursor states have been experimentally evaluated. The predissociation probability of the ionic state by adiabatic curve crossing has been estimated to describe the observed spectral intensity. A new kinetic model has been developed to describe the photoionization of CsF vapor. The calculated number density of the Cs\sp{2+}F\sp- ionic state of 6 ×\times 10\sp{13} cm\sp{-3} is in good agreement with the measured one. Based on the kinetic model, it is concluded that a CsF ionic excimer laser is feasible when a short pulse excitation with a line focusing geometry is employed. The absorption spectra of CsF, CsCl, and RbF in the UV and VUV have been determined using a VUV plasma continuum probe light source. The observed spectral peaks have been identified as the transitions from the ground states to the neutral covalent states. The spectra have been analyzed using the reflection method, providing potential curves of the neutral covalent states. The absorption oscillator strengths of these transitions have been evaluated from the absorption spectra

    Picoliter Cuvette inside an Optical Fiber to Track Gold Nanoparticle Aggregation for Measurement of Biomolecules

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    This study demonstrated a measurement approach for biomolecules at the picoliter scale, using a newly developed picoliter cuvette inside an optical fiber constructed via near-ultraviolet femtosecond laser drilling. The sensing capacity was estimated to be within 0.4–1.2 pL due to an optical path length of 3–5 microns, as measured by scanning electron microscopy (SEM). The picoliter cuvette exhibited a change in the optical extinction spectrum after addition of biomolecules such as L-cysteine, in conjunction with a gold nanoparticle (GNP) dispersion solution, following a simple measurement configuration involving a small white light source and a compact spectrometer. A linear attenuation of the spectral dip near a wavelength of 520 nm was observed as the L-cysteine concentration was increased at 4 wt% of the GNP mass concentration. The measurement resolution of the concentration using the picoliter cuvette was evaluated at 0.125 mM. The experimental results showed the difference in aggregation processes caused by a different concentration of GNPs. Moreover, they revealed the ability of the picoliter cuvette to verify whether the concentration of GNPs in the liquid sample correspondingly determines homogeneous or inhomogeneous GNP aggregation, as supported by SEM observation and numerical calculations based on Mie theory

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