Industry veteran Howard Mark and Spectroscopy Technical Editor Steve Brown present a timeline of both spectroscopy and Spectroscopy
This list of milestones is intended to be part of a celebration of 25 years of publication of Spectroscopy and is a summary of significant events in spectroscopy — as well as Spectroscopy — during this period. We made a reasonable attempt to identify the most significant developments in the various spectroscopies (optical, mass, and so forth), both in development of entirely new technologies as well as significant developments in instrumentation. We make no claim, however, for completeness. Also, some experts in the various fields may disagree with the experts we consulted as to the significance of some of the developments included, but we're reasonably sure that none of them are unimportant.
Some notes on the timeline follow. Many aspects of spectroscopy's history go back hundreds of years, such as Huygen's proposal of the wave theory of light. To be consistent with the concept of celebrating 25 years of Spectroscopy , however, we limit our window to the period from 1986 (when volume 1 of Spectroscopy was published) to today. Thus, such relatively recent and arguably more important work, such as Einstein's explanation of the photoelectric effect, and Digilab's development of the FTS-14, the first commercial Fourier transform (FT)-IR instrument, have to be left out. For those interested in tracing the history of spectroscopy back further than this review goes, other lists and timelines are available. Specific ones, limited to one or only a few technologies are available. See, for example, reference 1, which covers atomic spectroscopy. A timeline for Raman spectroscopy consisting of a PDF file containing Fran Adar's PowerPoint presentation at the Waters Symposium at the 2003 Pittcon starts at 1920 and includes developments up to the time of its presentation (2). Other, more general ones covering many different spectroscopies also exist. See reference 3, for example, which starts with Newton's discovery, in 1671, that sunlight can be broken up into its constituent colors with a prism.
The selected items included here are of necessity both eclectic and idiosyncratic. In words of one syllable or less, that means that we selected those advances for inclusion that struck us, or our advisory team, as being important. Others may differ as to the relative importance of various concepts or instruments (that's a disclaimer, folks). They are also incomplete. There's only so much that can be packed into one article.
Where possible, supporting information, usually in the form of a literature citation or a patent, verifies the time a given instrument or concept became available, but for some important developments, only the word of an expert in the field was available. In the case of patents, the date a patent was filed is considered the date the concept or device was developed, although in some cases, we report the date the patent was issued. Anyone interested enough can verify these at the patent office website, located at: http://www.uspto.gov
Some references to early literature are included, but the bibliography is not necessarily comprehensive. We attempt to provide information for further reading in various areas, by providing a very brief synopsis of work done before the timeline begins.
Atomic spectroscopy: There are some previous compilations in various areas that an interested reader may wish to consult. In the area of atomic spectroscopy, for example, Volker Thomsen has published an extensive timeline of just those advances relevant. Interested readers may consult it for a more detailed timeline covering a longer time span (1).
Optical imaging spectroscopy: Much development was initially done under government auspices, developing imaging for remote-imaging satellites like AVIRIS (see, for example, reference 4). Two intrepid members of our spectroscopic community, Neil Lewis and Patrick Treado, initially worked together under government auspices (5,6), then commercialized the imaging concept by each forming their own company, to become commercial competitors.
There were a fair number of Nobel prizes won that are based, one way or another, upon spectroscopy. We include those because they are, ipso facto, milestones in their own right, or at least represent major breakthroughs in their underlying science.
We start our timeline close to home, with something we expect most of our readers will be familiar with, namely, the people at Spectroscopy that they have seen, or they may have dealt with if they were an author. We continue with the instrumentation that has been developed and improved over these years.
January: Volume 1, issue 1 of Spectroscopy is published. Founding editor-in-chief is Heather Lafferty. (See Figure 1 for the table of contents for that initial issue.) Other editors through the years are
January 1988: Jane Ellis
October 1988: Mike MacRae
January 1991: Linda Crabtree
February 1994: Sherrie Steward
January 1995: Melissa Moseley
March 1995: Nancy Spurling Johnson
November 1995: Janaya Reitz
July 1998: Mike MacRae (returning after a stint at Wiley books)
July 1998: Gloria Goskie
January 2000: Michelle Nicolson
April 2000: Joe Perry
March 2005: David Walsh (editor-in-chief)
May 2006: Helen Castro
John Coates reminisced a bit about his role in the founding of Spectroscopy :
"You may not know this, but I was in part responsible for the formation and launch of Spectroscopy magazine. At the time, I was attempting to put together a similar publication working with Marcel Dekker. In fact, I had put together an entire editorial board. Heather Lafferty, the first editor of Spectroscopy, got wind of this and contacted me and asked my opinion of producing a magazine focused on spectroscopy . . . at the time, it was under the umbrella of Aster Publications in Eugene, Oregon. We discussed what we were both doing and we agreed to collaborate. From there, we gave birth to Spectroscopy magazine. I was the first column editor with the 'Molecular Spectroscopy Workbench.'
Just thought you should know the history of why the magazine was formed and who was involved in its formation."
I have encouraged John to write up his role of initiating Spectroscopy in more detail and submit it as a future article for publication and he has agreed to do so. Keep your eyes open!
The founding Editorial Advisory Board that John referred to consisted of:
Almost simultaneously with the initial publication of Spectroscopy , Bruce Chase and Tomas Hirschfeld developed and presented their seminal work on Fourier transform-Raman spectroscopy (7,8).
April 24: Tomas Hirschfeld passed away. Tomas was arguably the most well-known spectroscopist in the spectroscopic community, being active in all types of optical spectroscopy.
This year also marks Isao Noda's beginning to publish a series of papers developing the concept of 2-D correlation spectroscopy (9–15).
"Detection of Mass 16241 Ions by Fourier-Transform Mass Spectrometry" (16). FT-MS was already known.
"Ion Mobility Spectrometry/Mass Spectrometry of Some Prescription and Illicit Drugs" (17).
First column in the ongoing series "Statistics in Spectroscopy" published in January issue. Series title changed in 1993 to "Chemometrics in Spectroscopy."
"A System for Collecting High-Resolution Time-of-Flight Mass Spectrometric Data" (18).
"Excimer Laser Desorption Mass Spectrometry of Biomolecules at 248 and 193 nm" (19).
"Use of a Quadrupole Ion Trap in Mass Analysis Development of MALDI" (20).
The first fully computer-controlled inductively coupled plasma–mass spectrometry (ICP-MS) system (Yokogawa Plasma mass spectrometer).
Development of quadrupole ion trap gas chromatography (GC)–MS system.
"Hadamard Transform and Enhancement in Measurement of Tandem Fourier Transform Mass Spectra" (21).
"Ion Spray Interface for Combined LC/Atmospheric Pressure Ionization MS" (22).
"Capillary Zone Electrophoresis-MS" (24).
"Tandem Fourier Transform Mass Spectrometry" (25).
Early description of instrumentation for cavity ringdown spectroscopy (26). "Cavity Ring-Down Optical Spectrometer for Absorption Measurements Using Pulsed Laser Sources" (27,28).
Invention of radio-frequency glow-discharge source by M. Chevrier and Richard Passetemps.
High-end UV-Vis-NIR analytical spectrophotometers designed to take accessories, developed. These include the Perkin-Elmer Lambda 9/19/900/950 Series and the Varian (Cary) 5/500/5000 series. These instruments and the wide variety of measurement accessories for them open up analytical spectroscopy to the makers of thin films, coatings, paints, and so forth.
Nobel Prize in Physics to Norman F. Ramsay for atomic clocks, which are spectroscopy-based.
Wolfgang Paul shares Nobel Prize in Physics "For the development of the ion trap technique."
Richard McCreery first applies charge-couple device (CCD) detectors to Raman spectroscopy.
"FT-Raman Microscopy: Discussion and Preliminary Results"; Robert G. Messerschmidt and D. Bruce Chase. First spectra from a combined FT-IR/FT-Raman instrument (29).
"Matrix-Assisted Laser-Desorption Mass Spectrometry Using 355 nm Radiation" (30).
Perkin-Elmer announces the first self-contained (in other words, benchtop) FT-IR spectrometer. This represents the first important step toward miniaturization of spectrometers.
Detection of single molecules by W. E. Moerner using absorbance and then fluorescence measurements (31).
"Electrospray Interface for Liquid Chromatography/Mass Spectrometry" (32).
"The Utilization of a Holographic Bragg Diffraction Filter for Rayleigh Line Rejection in Raman Spectroscopy": first report of holographic laser-rejection filter for Raman spectroscopy in a commercial instrument (33).
Spectrometer for NIR based upon polarization interferometer is developed and patented (34,35), although the polarization interferometer itself can traced back to at least 1973 (36).
Nobel Prize in Chemistry to Richard R. Ernst for work in high-resolution nuclear magnetic resonance spectroscopy.
First high-resolution analytical diode array spectrophotometers developed by Hewlett-Packard (now Agilent). While diode arrays had been used in the color industry for years, these instruments, with a narrow bandpass and high stability, were a leap in technology for the analytical chemist.
Patent application filed for first diamond single-bounce ATR sampling accessory ("Radiant Energy Spectroscopy System Diamond Internal Reflection Element") Patent issues in 1993 (37).
Shield Torch technology is developed. This reduced secondary discharge allowing cool plasma measurements of previously unavailable isotopes such as 40Ca, 39K, and 56Fe, revolutionizing ultratrace analysis of these elements in the semiconductor industry.
Ocean Optics was founded in 1989. By April 1992, just 30 days after the successful completion of a Phase II SBIR grant, the company has introduced the S1000, the first miniaturized spectrometer, which was built on a computer plug-in board and announced this year. It was first shown it to the world at the 1993 Pittcon. There was such a crowd around the booth to see this marvel that the aisle was completely blocked, passers-by had to go around the aisle.
Step-scanning interferometric spectroscopy. IR step-scan spectroscopy becoming common in applications for time-resolved spectroscopy (38–44). This was not only useful in itself, e.g., for kinetics studies, it was also an enabling technology for multiple modulation experiments (dynamic infrared dichroism, easier photoelastic modulation), step-scan photoacoustic experiments and IR imaging using 2-D focal plane arrays.
This year saw the first commercially-available one-piece handheld XRF analyzer
The Leybold-Infinicon Hapsite is generally considered to be the first truly self-contained and man-portable GC–MS instrument (45).
May 13: Patent application for "DiComp" ATR, the first commercially successful Diamond ATR accessory. Patent 5,522,604, issued September 3, 1996 to Don Sting and Milan Milesovic.
Nobel Prize in Physics to Bertram N. Brockhouse and Shull for development of neutron spectroscopy.
June 18: Patent for imaging spectroscopy filed (6).
First ever benchtop ICP-MS system, the HP-4500. ICP-MS instruments were size reduced from huge, floor standing devices.
MS-MS in 3D QIT system.
Wikipedia reports on terahertz spectroscopy (46): "The first images generated using terahertz radiation date from the 1960s; however, in 1995, images generated using terahertz time-domain spectroscopy generated a great deal of interest, and sparked a rapid growth in the field of terahertz science and technology. This excitement, along with the associated coining of the term 'T-rays,' even showed up in a contemporary novel by Tom Clancy."
"FTIR Spectroscopic Imaging Using an Infrared Focal-Plane Array Detector" (47). This constitutes the first announcement of FT-IR imaging.
"Spectroscopic Imaging Device Using Imaging Quality Spectral Filters" (5,6).
Ira Levin and Curt Marcott develop IR microscopy.
Bio-Rad/Digilab first commercial FT-IR imaging system (NIR with InSb detector).
Bio-Rad/Digilab first commercial FT-IR imaging system (Mid-IR with MCT detector): "Digital Signal Processing for Step-Scan Fourier Transform Infrared Photoacoustic Spectroscopy" (48,49).
Although surface-enhanced Raman spectroscopy was first reported in 1980 (50), there is strong opinion that Osawa's paper, published 17 years later is really the seminal one (51).
Nitrogen-filled/flushed UV optical system developed and patented. See: "Vacuumless Spectrochemistry in the Vacuum Ultraviolet" (52).
Nobel Prize in Chemistry to Walter Kohn and John Pople for advanced in computational chemistry and density functional theory, which are widely used to predict spectroscopic properties.
"Three-Dimensional Ion Mobility/TOFMS Analysis of Electrosprayed Biomolecules" (53).
Founding of Spectral Dimensions, one of the commercial implementers applying the early remote-sensing imagers to analytical practice (54).
"Electrophoresis Combined with Novel Mass Spectrometry Techniques: Powerful Tools for the Analysis of Proteins and Proteomes" (55).
Kinetic FT-IR imaging: "Application of Real Time Mid-Infrared FTIR Imaging to Polymeric Systems. 1. Diffusion of Liquid Crystals into Polymers" (56).
Axsun Technologies founded, designs true microscopic spectrometers using semiconductor fabrication technology; Fabry-Perot interferometer, lenses and detector all made monolithically (57,58).
WITec sold its first Raman imaging system, the model CRM 200.
Nobel Prize in Chemistry to Ahmed Zewail for advances in laser femtosecond spectroscopy.
"New Procedure for Quantitative Elemental Analysis by Laser-Induced Plasma Spectroscopy" (59); initial presentation of LIBS.
"Fourier Transform Ion Cyclotron Resonance Mass Spectrometry in a High Homogeneity 25 Tesla Resistive Magnet" (60).
Miniature, low-power X-ray tube developed.
The TravelIR, the first (practical, man-) portable FT-IR is introduced by SensIR (now Smith's Detection) at this year's Pittcon (61).
"Dual Polarization Modulation: A Real-Time, Spectral-Multiplex Separation of Circular Dichroism from Linear Birefringence Spectral Intensities" (62).
The first generation Octopole mass spectrometer introduced by Agilent. This allowed kinetic energy discrimination using an inert gas to eliminate polyatomic interferences without prior knowledge about the sample composition.
Polychromix founded, developed "Digital Transform" spectrometer (63).
"Apparatus and Method for Real Time IR Spectroscopy" (64) for John Rabolt planar array, non-FTIR, spectrometer, Initial patent filed Aug, 2001, issued 2004.
"Picosecond Time-Resolved Raman Spectroscopy of Solids: Capabilities and Limitations for Fluorescence Rejection and the Influence of Diffuse Reflectance" (65).
LAN control as opposed to GPIB control allowed simpler connectivity over longer distances between the computer and ICP-MS instrument.
John Fenn and Koichi Tanaka share Nobel Prize in Chemistry for "for the development of methods for identification and structure analyses of biological macromolecules" and "for their development of soft desorption ionization methods for mass spectrometric analyses of biological macromolecules."
The first commercial GC–ICP-MS interface introduced by Agilent, allowing routine speciation analysis of ultratrace elements in volatile materials.
"Generalized Implementation of Rapid-Scan Fourier Transform Infrared Spectroscopic Imaging" (66).
Patent 6,943,353 "Simultaneous Multi-Beam Planar Array IR (PAIR) Spectroscopy" patent for PAIR spectroscopy filed. Issued 2004 (67).
Bayspec develops the Volume Phase grating (68).
The linear quadrupole ion trap is developed.
First application of collision/reaction cell inductively coupled plasma mass spectrometry to multielement analysis in variable sample matrices, using He as a nonreactive cell gas (69).
"The Orbitrap: A New Mass Spectrometer" (70).
Nobel Prize in Physics to John L. Hall and Theodore W. Hansch for advances in laser spectroscopy.
Nobel Prize in Physics to John C. Mather and George F. Smoot for discovery and understanding of cosmic background radiation, detected using microwave spectroscopy.
"Latent Fingerprint Chemical Imaging by Mass Spectrometry" (71).
October 11: Paul Wilks passes away. Paul was responsible for the design of many mid-IR and near-IR spectrometers, first at Perkin-Elmer, then at several companies he founded.
Nobel Prize in Physics to Willard S. Boyle and George E. Smith for their development of the CCD, an important detector used in spectroscopy and other optical devices (like digital cameras).
July 30: Bill Fateley passes away. Bill was the long-time editor of Applied Spectroscopy ; everyone in the spectroscopic community knew and liked him.
The authors gratefully acknowledge the assistance and contributions of the many experts in the various technologies who provided information included here, in bringing important information to our attention and giving advice on what to include (note, however, that we made the final selections and take all responsibility for them). In alphabetical order, these are David Ball, Shawn Briglin, Chris Brown, Bruce Chase, John Coates, Richard Crocombe, Harald Fischer, Mike Grayson, Peter Griffiths, David Haaland, Richard Larsen, E. Neil Lewis, Marvin Margoshes, Alan Rein, Ron Rubinovitz, David Schiering, David Sparkman, Art Springsteen; Volker Thomsen, and Steven Wilbur.
Howard Mark is with Mark Electronics, Suffern, New York, and Steve Brown is Spectroscopy's technical editor.
(1) V. Thomsen, Spectroscopy 21 (10), 32–42 (2006).
(4) A.F.H. Goetz, G. Vane, and J.E. Solomon, Science 228 (4704), 1147–1153 (1985).
(5) E.N. Lewis, I.W. Levin, and P.J. Treado, Spectroscopic Imaging Device Using Imaging Quality Spectral Filters, U.S. Patent 5,377,003, 12/27/1994.
(6) E.N. Lewis, I.W. Levin, and P.J. Treado, "Spectroscopic Imaging Device using Imaging Quality Spectral Filters", U.S. Patent 5,528,368, 06/18/1994.
(7) B. Chase and T. Hirschfeld, Appl. Spectrosc. 40 (2), 133 (1986).
(8) B.D. Chase, J.ACS 108, 7485–7488 (Nov. 26, 1986).
(9) I. Noda, Bull. Am. Phys. Soc. 31, 520 (1986).
(10) I. Noda, Appl. Spectrosc. 44, 550 (1990).
(11) I. Noda, J. Am. Chem. Soc. 111, 8116 (1989).
(12) I. Noda, A.E. Dowrey, and C. Marcott, Abstr. Pap. Am. Chem. Soc. 202, 117 (1991).
(13) I. Noda, Appl. Spectrosc. 47, 1329 (1993).
(14) I. Noda, A.E. Dowrey, and C. Marcott, Appl. Spectrosc. 47, 1317 (1993).
(15) I. Noda, Appl. Spectrosc. 54, 994 (2000).
(16) M.E. Castro, D.H. Russell, I.J. Amster, and F.W. McLafferty, Anal. Chem. 58, 483–485 (1986).
(17) A.H. Lawrence, Anal. Chem. 58, 1269–1272 (1986).
(18) L.I. Grace, B.T. Chait, and F.H. Field, Biomed. Environ. Mass Spectrom. 14, 295–299 (1987).
(19) B. Spengler, M. Karas, U. Bahr, and F. Hillenkamp, J. Phys. Chem. 91, 6502–6506 (1987).
(20) W.J. Fies, Jr., P.E. Kelley, W.E. Reynolds, G.C. Stafford, Jr., and J.E.P. Syka, Patent 84663314.
(21) F.W. McLafferty, D.B. Stauffer, S.Y. Loh, and E.R. Williams, Anal. Chem. 59, 2212–2213 (1987).
(22) A.P. Bruins, T.R. Covey, and J.D. Henion, Anal. Chem. 59, 2642–2646 (1987).
(23) A.P. Bruins, T.R. Covey, and J.D. Henion, Anal. Chem. 59, 2642–2646 (1987).
(24) R.D. Smith and H.R. Udseth, Nature 331, 639-640 (1988).
(25) F.W. McLafferty, E.R. Williams, B.H. Wang, J.A. Loo, S.Y. Loh, and K.D. Henry, Anal. Proc. 25, 358–359 (1988).
(26) A. O'Keefe and D.A.G. Deacon, Rev. Sci. Instrum. 59, 2544 (1988).
(28) G. Berden, R. Peeters, and G. Meijer, Int. Rev. Phys. Chem. 19 (4), 565–607 (2000).
(29) R.G. Messerschmidt and D.B. Chase, Appl. Spectrosc. 43, 11–15 (1989).
(30) R.C. Beavis, B.T. Chait, and K.G. Standing, Rapid Commun. Mass Spectrom. 3, 436–439 (1989).
(31) W.E. Moerner, Anal. Chem. 61, 1217A–1223A (1989).
(32) K. Hiraoka and I. Kudaka, Rapid Commun. Mass Spectrom. 4, 519-526 (1990).
(33) M. Carrabba, K.M. Spencer, C. Rich, and D. Rauh, Appl. Spectrosc. 44 (9), 1558–1561 (1990).
(34) H. Wagner, M. Labhart, and U. Glaus, Polarization interferometer spectrometer; Patent 5,157,458; Application filed Nov 2, 1990, patent issued October 20, 1992.
(35) T. Meyer, J. Oelichmann, and H. Kellerhals, Trends Anal. Chem. 25 (1), 19-23 (2006).
(36) R.C. Hawes, Polarization interferometer with beam polarizing compensator; Patent 3,737,325; issued June 5, 1973.
(37) Patent 5200609 filed in 1991 to Don Sting for single-bounce diamond ATR, "Radiant Energy Spectroscopy System Diamond Internal Reflection Element." Patent issued in 1993.
(38) C.J. Manning and P.R. Griffiths, Appl. Spectrosc. 47 (9), 1345 (1993).
(39) R.A.Palmer, J.L. Chao, R.M. Dittmar, V.G. Gregoriou, and S.E. Plunkett, Appl. Spectrosc. 47 (9), 1297–1310 (1993).
(40) V.G. Gregoriou, M. Daun, M.W. Schauer, J.L. Chao, and R.A. Palmer, Appl. Spectrosc. 47 (9), 1311–1316 (1993).
(41) T. Nakano, T. Yokoyama, and H. Toriumi, Appl. Spectrosc. 47 (9), 1354–1366 (1993).
(42) T.J. Johnson, A. Simon, J.M. Weil, and G.W. Harris, Appl. Spectrosc. 47 (9), 1376–1381 (1993).
(43) J.R. Burie, W. Leibl, E. Nabedryk, and J. Breton, Appl. Spectrosc. 47 (9), 1401–1404 (1993).
(44) C.J. Manning and P.R. Griffiths, Appl. Spectrosc. 47, 1345 (1993).
(45) Patent 5426300, application filed September 17, 1993, issued 1995, to G. Voss, S.J. DeLuca, and G. Adams.
(47) E.N. Lewis, P.J. Treado, R.C. Reeder, G.M. Story, A.E. Dowrey, C. Marcott, and I.W. Levin, Anal. Chem. 67, 3377 (1995).
(48) D.L. Drapcho, R. Curbelo, E.Y. Jiang, R.A. Crocombe, and W.J. McCarthy, Appl. Spectrosc. 51, 453–460 (1997).
(49) D.L. Drapcho, R. Curbelo, R.A. Crocombe, and D.F. Johnston, "Digital signal processing techniques for multiple modulation FT-IR measurements," in Fourier Transform Spectroscopy: Twelfth International Conference, K. Itoh and M. Tasumi, Eds. (Waseda University Press, Tokyo, Japan, 1999), pp. 203–204.
(50) A. Hartstein, J.R. Kirtley, and J.C. Tsang, Phys. Rev. Lett. 45, 201–204 (1980).
(51) M. Osawa, Bull. Chem. Soc. Jpn. 70, 2861–2880 (1997).
(52) V. Thomsen, G. Roberts, and D. Tsourides, Amer. Lab. 29 (16), 18H-M (August 1997).
(53) C.S. Hoaglund, S.J. Valentine, C.R. Sporleder, J.P. Reilly, and D.E. Clemmer, Anal. Chem. 70, 2236–2242 (1998).
(54) P.J. Treado, I.W. Levin, and E.N. Lewis, Appl. Spectrosc. 46, 1211 (1998).
(55) D. Figeys, S.P. Gygi, Y. Zhang, J. Watts, M. Gu, and R. Aebersold, Electrophoresis 19, 1811–1818 (1998).
(56) C.M. Snively and J.L. Koenig, Macromolecules 31, 3753–3755 (1998).
(57) R.A. Crocombe, D.C. Flanders, and W. Atia, Proc. SPIE 5591, 11–25 (2004).
(58) P. Kotidis, W. Atia, M. Kuznetsov, S. Fawcett, D. Nislick, R. Crocombe, and D.C. Flanders, "Optical, Tunable Filter-Based Micro-Instrumentation for Industrial Applications," ISA Technical papers Collection (The Instrument, Systems and Automation Society), Volume 439 (2003).
(59) A. Ciucci, M. Corsi, V. Palleschi, S. Rastelli, A.Salvetti, and E. Tognoni, Appl. Spectrosc. 53 (8), 960–964 (1999).
(60) S.D-.H. Shi, J.J. Drader, C.L. Hendrickson, and G. Ma, J. ASMS 10, 265–268 (1999).
(61) Patent 5552604 application filed in 1994 by Don Sting and Milan Milosevic, patent issued in 1996.
(62) L.A. Nafie, Appl. Spectrosc. 54 (11), 1634–1645 (2000).
(63) Y. Geller and M. Ramani, Proc. SPIE 5970, 306–312 (2005).
(64) United States Patent 6,784,428 Filed October 21, 2001, issued August 31, 2004.
(65) N. Everall, T. Hahn, P. Matousek, A.W. Parker, and M. Towrie, Appl. Specrosc. 55 (12), 1701–1707 (2001).
(66) S.W. Huffman, R. Bhargava, and I.W. Levin, Appl. Spectrosc. 56 (8), 965–969 (2002).
(67) Patent 6,943,353, "Simultaneous multi-beam planar array IR (PAIR)
spectroscopy" patent application for PAIR spectroscopy filed by D.L. Elmore, J.F. Rabolt, and M-.W. Tsao; application filed April 1, 2004. Patent issued September 13, 2005.
(68) Patent 6,747,791 – Volume Phase grating, application filed December 3, 2002, patent issued June 8, 2004, to W.W. Yang, L. Chen, F.H. Levinson, D.D. Yu, C.S. Zhang, C.C. Wang, and W.W. Liu.
(69) E. McCurdy and G. Woods, J. Anal. Atom. Spectrom. 5, 607–615 (2004).
(70) Q. Hu, R.J. Noll, H. Li, A. Makarov, M. Hardman, and R.G. Cooks, J. Mass Spectrom. 40, 430–443 (2005).
(71) D.R. Ifa, N.E. Manicke, A.L. Dill, and R.G. Cooks, Science 321, 805 (2008).