Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrophotometer
Reexamination Certificate
2000-09-14
2004-05-25
Rosenberger, Richard A. (Department: 2877)
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrophotometer
C356S325000, C356S318000
Reexamination Certificate
active
06741347
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of laser flash photolysis, and in particular, the present invention provides a novel miniaturized laser flash photolysis system, with improved performance over existing laser flash photolysis systems.
Laser flash photolysis (LFP) is a technique utilized to study reaction mechanisms in chemical and biological processes. The technique was introduced in 1966 by Lindqvist at the CNRS in France and quickly developed by various research groups around the world.
FIG. 1
shows a schematic drawing of this original set up. It can be regarded as a technical development of what is now called “conventional flash photolysis”. The development was brought about by the invention of the laser, in the early 1960s.
The technique of LFP, as it has been utilized for the last twenty years (FIG.
2
), consists of a pulsed laser source that generates the chemical species to be studied, an optical and electronic system capable of sensing optical changes in the sample, and a computer suitably equipped to capture, process and display the data.
The optical and electronic system mentioned above are the heart of any LFP system. They essentially constitute a fast spectrometer capable of acquiring spectra of very short lived chemical species called “intermediates”, and recording their evolution with time, that is, their kinetics. The present invention deals specifically with this part, and can be used with most modem pulsed lasers. Moreover, in order to measure kinetics only, a spectrometer is not required, or the instrument can be used at a fixed wavelength setting.
LFP techniques have evolved over the years to include time resolutions as short as femtosecond (10
−15
seconds). The invention described here refers to systems with nanosecond resolutions, which usually use lasers with pulse durations between 1 and 20 ns, although the concept is not restricted to this time scale. The detection components of such an LFP system are based on commercial photomultiplier tubes (PMT) and have adequate responses from about 1 nanosecond to macroscopic time scales, although LFP systems are rarely utilized in time scales longer than 1 second.
The term LFP usually refers to the optical and electronic components mentioned above, and practitioners of the technique understand that in addition to the LFP system, a functional instrument also requires a pulsed laser and a computer. Modem LFP systems have a typical footprint of 10 square feet, frequently slightly bigger; this footprint is exclusive of space taken by the laser and the computer. The LFP system is normally mounted on an optical table, or a solid and firm table; such an LFP system is not portable. Transportation normally involves taking apart dozens of components which need to be reassembled, reconnected and properly aligned following any move.
The invention consists of the development of a new miniature laser flash photolysis system (mLFP) which represents a major improvement over existing apparatus. Three aspects of this new mLFP system are important in this regard:
(i) A great reduction in the overall size of the instrument, which has a footprint of less than 2 square feet.
(ii) In contrast with all existing systems, the new set-up is readily portable. It consists of integrated components in an enclosure with a footprint of 12 inches by 18 inches, plus a small digitizer which connects to the enclosure mentioned above and the computer.
(iii) By incorporating an innovative optical design around the sample holder, the new mLFP system does not require “pulsing” the monitoring lamp and is virtually insensitive to scattered light and fluorescence. Scattered light and fluorescence represent major problems in prior LFP methods;
(iv) The instrument lends itself easily to remote sensing, by taking advantage of optical fibers of variable length.
In a broad aspect, then, the present invention relates to an apparatus for flash photolysis including: i) a source of light radiation; ii) optical means for channeling light from said source through a sample; iii) means to initiate a chemical change in said sample; iv) means for measuring the change in absorption of said light radiation by said sample during said chemical change.
REFERENCES:
patent: 3811777 (1974-05-01), Chance
patent: 3901600 (1975-08-01), Johnson, Jr et al.
patent: 4023905 (1977-05-01), Chance
patent: 869465 (1996-10-01), None
Ebbesen, Review of Scientific Instruments, vol. 59, No. 8, p. 1307-1309 (Aug., 1988).
Charette Gerry
Scaiano Juan C.
Simard Andre
Barth Vincent P.
Casella Anthony J.
Hespos Gerald E.
Rosenberger Richard A.
University of Ottawa
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