J. P. Young

Observation of the Surface-Enhanced Raman Scattering Spectrum of Uranyl Ion

We wish to report the surface-enhanced Raman scattering (SERS) spectrum of uranyl ion, as a uranyl nitrate complex. The uranyl-ion group has a very characteristic linear structure. The oxygen-uranium bond in this group is known to be only slightly weaker than that of the carbon-oxygen in CO2. The vibrational frequency of the symmetric stretch for the uranylion is Raman active and is located around 800 Δcm-1 , varying with compounds, There has been a previous Raman and SERS study of uranyl superphthalocyanine (UO2SPc). That study dealt primarily with ligand interactions but did note a unique interaction of the UO2SPc molecule and silver. A weak SERS enhancement of less than 102 was noted; the weak enhancement was believed to be caused by damping effects of the superpthalocyanine molecule. To our knowledge, our work is the first to show a SERS enhancement for an inorganic species, UO2(NO3)2, on silver.

Quantitative Raman Spectral Measurements Using a Diamond-Coated All-Silica Fiber-Optic Probe:

To conduct quantitative Raman analyses, it is very important to keep the same experimental conditions when analyzing different samples; very often this is dif® cult to accomplish. Further, optical conditions such as laser power, optical alignment, and coupling change with time. These changes affect the intensity of a given signal and, ultimately, the accuracy of determination. To carry out quantitative measurements by Raman spectroscopy, one must normalize the intensity of a suitable Raman emission from a sample species to a Raman signal from some invariant species present in or added to the sample matrix. Theoretically, the Rayleigh line is a suitable reference for the normalization; however, the Rayleigh line is too strong relative to Raman signals. For cases when the Rayleigh line is broad, such as in samples at elevated temperature, a procedure has been reported1 for normalizing spectra by using a position of the Rayleigh scatter curve shifted from 0 cm2 1. In this note, we wish to report another technique that normalizes Raman spectra for quantitative measurements. We have developed an all-silica ® ber-optic probe that is fabricated by fusing optical ® bers inside a quartz tube under vacuum.2,3 This probe works very well for obtaining the Raman spectra for many systems.3,4 Recently, the

Prediction and Identification of Multiple-Photon Resonant Ionization Processes

Many single-color, multiple-photon transitions leading to ionization are observed for lanthanide and actinide elements in experiments using resonance ionization mass spectrometry (RIMS). It is desirable both to identify the energy levels involved in observed transitions and to be able to predict in advance their location. A computer code, ETRANS, has been written to perform these functions. Examples of both types of operation are given.

Reduction of Fused-Silica-Fiber Raman Backgrounds in High-Temperature Fiber-Optic Raman Spectroscopy via the Measurement of Anti-Stokes Raman Spectra

Measurements of laser Raman spectroscopy using optical fibers have recently become an active area of study. The technique requires minimum alignment of samples with respect to an input laser beam or collection optics, and the sample may be located some distance from the spectrometer in a hostile environment. Most fiber-optic probes employed for such spectroscopic measurements have been constructed by sealing the collecting fibers and one input fiber into a metal or glass protective tube with a special kind of epoxy cement. These materials in a probe impose difficulties in the collection of spectra in some hostile chemical environments because of chemical reactions of the epoxy resin with the surrounding environment. Recently we have reported the fabrication of an all-fused-silica fiber-optic probe that is useful for measuring Raman spectra of molten salt systems at high temperature. A drawback of fiber-optic remote Raman spectroscopy is the large background Raman signals generated from the optical fiber itself. Therefore, the major requirement of remote Raman spectroscopy is the reduction of the unwanted background signals to a level below that of the sample Raman signals. Myrick and Angel have reported the use of optical interference filters to filter out the background fiber signals. In that study, a bandpass filter was used at the tip of the excitation optical fiber to reject any fluorescence or unwanted background signals from the excitation fiber, which, at the same time, allows transmission of the large portion of the laser beam. Similar techniques have also been employed by Sharma and his co-workers in their recent remote fiber-optic studies. Usually, these optical filters cannot survive high-temperature conditions. Here we want to report a simple and yet efficient method to minimize the fiber background signals for high-temperature remote Raman spectroscopy. The performance of the method was characterized by the measurement of Raman spectra of magnesium tetrachloride ion in a high-temperature molten salt medium.

Application of resonance ionization mass spectrometry to the lanthanide elements in the wavelength region of 430–455 nm

Abstract A study of all the lanthanides except promethium has been carried out using resonance ionization mass spectrometry; the wavelength region for this investigation was 430–450 nm. A list of several wavelengths is given for each of these lanthanides where they can be determined without isobaric interference of other lanthanides. The optical routes for ionization were cataloged in terms of 1+1,1+1+1, and 2+1 photon pathways where possible, and the known or partially known routes are presented. Possible pathways for the unknown optical routes are evaluated.

Spectral Study of Promethium and Samarium by Resonance Ionization Mass Spectrometry

A spectral study of promethium and samarium in the wavelength ranges of 530 to 560 and 580 to 615 nm has been made by resonance ionization mass spectrometry. A total of 54 promethium and 35 samarium ionization wavelengths were found. These optical routes are thought to involve a single-color, three-photon process. On the basis of this premise, new qualitative spectral information for both these elements is obtained from these data, and directions for more definitive studies result.

Diode laser-initiated, two-color resonance ionization mass spectrometry of lanthanum

A GaAlAs semiconductor diode laser tuned to 753.93 nm was utilized to excite the first step of three‐photon resonance ionization processes of lanthanum. A practical resonance ionization mass spectrometric (RIMS) instrument based solely on diode laser optical excitation is envisioned.