Joseph F. Becker

Stable isotope analysis using tunable diode laser spectroscopy

Measurements of ratios of stable isotopes are used in such diverse fields as petroleum prospecting, medical diagnostics, and planetary exploration. The narrow emission linewidth available from tunable diode lasers permits high-resolution infrared absorption measurements of closely spaced isotopic rovibrational lines. Our dual beam spectrometer uses the sweep integration technique in a spectral region where adjacent spectral lines are of approximately equal absorbance at the expected isotopic abundances. The experimental results reported here indicate that isotopic ratios of carbon in carbon dioxide can be measured to an accuracy of better than 0.4%. This laser spectroscopic technique offers an alternative to the mass spectrometric technique for in situ isotopic analysis in field studies, as well as flight and space applications.

Stable isotope laser spectrometer for exploration of Mars

On Earth, measurements of the ratios of stable carbon isotopes have provided much information about geological and biological processes. For example, fractionation of carbon occurs in biotic processes and the retention of a distinctive 2-4% contrast in 13C/12C between organic carbon and carbonates in rocks as old as 3.8 billion years constitutes some of the firmest evidence for the antiquity of life on the Earth. We have developed a prototype tunable diode Laser spectrometer which demonstrates the feasibility of making accurate in situ isotopic ratio measurements on Mars. This miniaturized instrument, with an optical path length of 10 cm, should be capable of making accurate 13C/12C and 15N/14N measurements. Gas samples for measurement are to be produced by pyrolysis using soil samples as small as 50 mg. Measurements of 13C/12C, 18O/16O and 15N/14N have been made to a precision of better than 0.1% and various other isotopes are feasible. This laser technique, which relies on the extremely narrow emission linewidth of tunable diode lasers (<0.001 cm(-1)) has favorable features in comparison to mass spectrometry, the standard method of accurate isotopic ratio measurement. The miniature instrument could be ready to deploy on the 2003 or other Mars lander missions.

Continuous monitoring of a changing sample by multiplex gas chromatography

Multiplex gas chromatography (MGC) is a technique in which multiple samples may be introduced into a chromatographic system regardless of the elution time of the individual components. Although the output obtained from a MGC experiment is not directly interpretable, computational techniques can be used to obtain the chromatogram from the detector output data. This is done by calculating the impulse response function from the multiplexed output data.

Fluorescence Lifetime Measurements of Mercury-Protein Complexes

Fluorescence lifetime and steady-state fluorescence measurements are used to characterize various mercury/protein and mercury/protein/EDTA complexes. The proteins studied are ovalbumin, α-chymotrypsinogen, and acid phosphatase. Mercury quenches fluorescence in ovalbumin with a change in lifetime, while in α-chymotrypsinogen quenching occurs without a change in lifetime. No quenching by mercury is observed for acid phosphatase. EDTA causes a further small decrease in fluorescence for both mercury/ovalbumin and mercury/α-chymotrypsinogen, while no change is observed for mercury/acid phosphatase. In all cases the decrease in fluorescence intensity is consistent with a static quenching mechanism. The results reported are correlated to previous studies by bromine-81 magnetic resonance spectroscopy.

Development of graduate level optoelectronics packaging courses at San Jose state university

A new graduate level curriculum to address the needs of the optoelectronic packaging industry has been proposed and is in the process of being developed. This effort builds on the interdisciplinary concentration area in microelectronic packaging that San Jose State University’s College of Engineering has been offering since January 1991. The current effort is also interdisciplinary and is being undertaken by the College of Engineering and the Physics Department. Two new courses will he developed Introduction to Optoelectronic Packaging, an engineering graduate level course and Principles and Applications of Optoelectronics, a

Optics program in the physics department at San Jose State University

The San Jose State University Physics Department, located in Silicon Valley, provides students with a high quality education in optics and provides local high-tech industry and government laboratories with a partner for optics- related research and development projects. There are approximately 50 undergraduate majors and 20 graduate (M.S.) students in the Department. Core courses leading to the B.S. in Physics are offered with upper division courses in Modern Optics, Lasers and Applications, Advanced Optics Lab, Advanced Instrumentation Lab, and Individual Studies as well as graduate courses in Electro-optics, Graduate Optics, Optical Metrology, and Laser Spectroscopy. Graduates are well prepared to enter the lasers and optics industry or go onto graduate school. A 4000 square-foot lab in the Science Building houses the Institute for Modern Optics, an organized research unit in the College of Science. One of the major goals of the Institute is to facilitate collaborative research between the local optics industry and the faculty and students at SJSU. The Department is presently developing a new biophotonics lab for single molecule studies with a dual beam optical tweezers already operational. A National Science Foundation Research Experience for Undergraduates Program grant provides research support for undergraduates.