NEWS & REVIEW

This, the last edition of 2001 has been delayed. No – not because your dear Editor has been overdoing it for Christmas, but rather because we have been hit by an announcement that I suppose was inevitable – Perkin Elmer have decided to cease their support of the Journal. Their announcement is as follows -

On 17^th December, Perkin Elmer informed me in a phone conversation that the Company was withdrawing financial support for IJVS. A meeting between Louise, Dr Dave Clark of Perkin Elmer and myself was held on 20^th at Seer Green, the UK Headquarters of Perkin Elmer and we went over the conditions of the withdrawal of support. The situation is complicated because P-E own the title and the copyright – I am the Editor but I don’t control the destiny of the Journal.

Clearly, to continue we need to obtain further financial support. Fortunately, Perkin Elmer have agreed to support the Journal until 31^st March 2002 giving us some time to come up with alternatives. It is also clear that P-E will release the title and copyright so that alternative supporters can be more easily arranged.

Our most pressing concern is to protect the archive – authors who have published or edited papers or feature articles in IJVS must be sure that readers’ have the ability to down-load their article. Perkin Elmer have volunteered to cover this by placing the IJVS archive on their website, but the problem is that citations would not be useful since the www.ijvs.com website might well be closed. However, we have already been able to arrange some sponsorship so that the website will continue until 1^st January 2011 whatever else happens. So – the archive is secure for 10 years.

Many different modes of support can be tapped – sole sponsorship by one manufacturer, multiple sponsorship, advertising etc, etc. Leave it to us to see what we can do and I will report in the next Editorial.

In late December we had four submitted papers being edited or going through the refereeing process. In view of the uncertainty over the future of your Journal we emailed all four sets of authors, explained the situation to them and asked them of they would like to withdraw their papers and publish them elsewhere. To our delight all four have replied enthusiastically that they want to publish in IJVS -

" I am sorry that the Journal has financial troubles and I am confident that you will manage to solve them in a satisfactory manner. It is important for the spectroscopy community to have this meeting place on the Internet, especially because it is really different from any other Journal. We don't withdraw, of course, our article and will wait that you solve the problems."


"I don't wish to withdraw the recently submitted paper to IJVS and I sincerely hope that you will succeed to find an alternative source of financial support."


"I am sorry to hear that PE may cease their sponsorship of IJVS. I do not want to withdraw my paper submitted to IJVS recently and hope this helps. I hope the negotiations go successfully to your favour."<


"As my work is in FTIR and spectroscopic area, and I like to publish it in IJVS, I will wait till you sort out the problem."

Although it is sad that Perkin Elmer are not going to support the Journal in future, we must thank the Company for making IJVS possible and for supporting us for so long.

In late November and during December, I attended a couple of excellent meetings. One, on December 13^th, was organised by the Infrared & Raman Discussion Group of the UK. This organisation has been around for the best part of 50 years and meets about 4 times a year. Every year the Christmas meeting is invariably held at King’s College in the Strand, bang in the middle of London and is organised around the lunch [Very Christmassy – very alcoholic* - very convivial]. Persuading people to give talks after the lunch has become an art-form, but this year the organisers were particularly effective and we had a full afternoon programme. Most of the members stayed awake proving that lecturing skill will prevail over all adversity!

* Invariably supplied by one of the major instrument companies.

On 20^th November I caught up with a one-day conference on the use of Raman in Art History and Archaeology. I’m no artist and have to admit that I’m not particularly interested (my obsession is with music) but this was one of the most fascinating meetings I have ever attended. Please read my report.

Finally, we have had some response from you with your pictures of where you work and live, a big thank you to those who have sent us stuff.. Here are the ones we've had.

	Now there's a view. This photo was sent in by Dr Michael Martin. It is the view from the Advanced Light Source Synchroton facility in Berkeley, California, overlooking Sam Francisco Bay area.
This pic was sent in from Eva Horn Møller from Denmark. She says " The Royal Danish School of Pharmacy in Copenhagen, Denmark dates from 1892 and moved to the present address in 1942. The newest building (shown right) was added in 1998. It offers state-of-the-art labs, an integrated art solution and a large spectrscopy cellar under that vividly green lawn"
	Our mate down under Ian Wesley sent in loads of pictures. Here's the place where he works - BRI Australia Ltd, and independent company that provides research to the Australian grain industry. Its also the home of the Grain Industries Centre for NIR Spectroscopy. The other picture is a small bridge in his 'home' town Sydney. We can see it's another miserable day 'down under'!
Finally in our latest selection, our great friend Professor Z.Q. Tian has sent us photos of his office (where hopefully he's writing us another paper!?) and his apartment block in Beijing.

Please keep the photos coming in. They really cheer me up seeing where some of you are and mostly blue skies, its certainly not 'blue skies' here in the UK at the moment, being the usual dark and drearly English wintertime - Louise.

2. Infrared & Raman
Discussion Group Meeting
Kings College London
December 13^th 2001

Editor

The IRDG holds 4 meetings each year, the Christmas one always being at King’s College in the Strand, London. The IRDG is a very well established organisation with about 185 members. It has held roughly this number of meetings over very many years. The Christmas meetings is always built around an excellent Christmas lunch, the booze being funded by one of the major instrument Companies. This year was Perkin Elmer’s turn.

Dr. J.A Reffner of SensIR in Danbury, Conn. Started the proceeding by giving us an overview of the vibrational spectroscopy business. He pointed out that the US sales were around $1.3 x 10⁸ and had been at this level for 1997-2000. On the other hand the US economy had done well in this period. The industry was mature. Its days of rapid expansion were over. Further, the US sales are split amongst 17 companies so no one is really large. At the end of Dr Reffner’s talk I pointed out that one of the reasons for the stagnation in the industry was that in Universities IR, Raman and NIR were simply not taught. The emphasis was on NMR and MS.He agreed that this is a problem.

Reffner then went on to describe a series of applications of IR in forensic work, usually involving IR microscopy. All were fascinating and some just plain gory! e.g. it seems that some lad in the US murdered his wife, froze the body and then sliced it up into logs with a chain saw. He then hired a wood chipping machine and yes, you’ve guessed it, chipped up the logs. It seems someone thought it was rather odd to be doing this in mid winter and the police took an unfriendly interest. Amazingly in all the mess a tiny piece of finger-nail was found and checked by IR microscopy. The nail varnish (polish) matched that found in the familial bathroom! Other examples involving investigations at the first World Trade Centre bombing and bullets then followed. Dr Reffner completed his talk with a description of his company’s IlluminateIR - a tiny instrument built onto a microscope and showed examples of its applications.

The theme of the meeting, 'new techniques and developments from the instrument manufacturers' was then developed by Dr Neil Lewis of Spectral Dimensions of Olney Maryland. Neils’ subject was array detectors and their use in infrared microscopy. He showed superb images of brain tissue taken with a mercury cadmium telluride array 1024 x1024 pixels in size. He pointed out that as products become more complex and/or people are moving into the biological field, the need for imaging at ever increasing resolution was growing. As an example, he showed a polymeric layer system where rogue inclusions could be analysed.

Using an NIR tuneable filter detector on a microscope, images can be examined to distinguish pseudo identical tablets, to explore mixing at interfaces or to study blending e.g. mixing excipient and active constituents in pharmaceutical products.

Dr Lewis then went on to show how contamination can be discovered in animal protein – a highly topical field of course in the UK. If the feed is thinly spread on a surface and the picture obtained in specific infrared wavelengths a particle of contaminant can be identified regardless of its overall bulk concentration.

To conclude, cost riased its ever present head. NIR arrays are reasonable in cost ~$0.30/pixel, but in the MIR there is a real problem. 64 x 64 pixels can cost as much as $35,000.

Contributions from the US continued with an account of new measurements in inelastic neutron scattering from Prof Bruce Hudson of the University of Syracuse. His interest in INS includes a variety of problems e.g. dodecahedron C₂₀H₂₀ an isosohedral and hence a highly symmetric molecule. Almost no modes appear in the IR and Raman – 11 in a total of 30 i.e. 19 are ‘silent. The INS spectrum has no selection rules and all are seen. It also seems that the frequencies and the intensity of the INS bands are ‘easy’ to predict. The point was demonstrated.

Hydrogen is an excellent (in fact overwhelming) neutron scatterer so the method is ideal for studying hydrogen bonding. The example of oxamide was shown.

Bruce Hudson also discussed the study of overtones in both neutron and resonance Raman scattering.

After the lunch, the unfortunate lecturers have to talk through an alcoholic fug and shout over the snores. Well our speakers were so interesting insomnia seemed to set in with a vengeance.

Robert Hoult of Perkin Elmer kicked off with a description of the company’s new imaging mid infrared microscopic instrument entitled Spotlight. I wont give an account here as the technology is subtle and if not explained carefully is hard to understand. Dr Hoult and his colleague Dr Richard Spragg have sent me material to write a feature on this new machine and it will appear in the next edition.

Prof.Howell Edwards then spoke last (not a particularly popular spot on the agendum). Howell gave a talk at the British Museum but this one was totally different. Howell Edwards works with the British Antartic Survey. On Antartica, there are areas incredible inhospitable to growth. There are dessert areas with almost zero humidity, at temperatures around -35ºC suffering high winds and exposed to intense UV radiation i.e. the sort of conditions as hostile as those that exist on Mars. Now, there is a plan to develop an ultra lightweight Raman instrument, which will be landed on Mars. A probe will sample the surface of the planet and the infrared instrument will search for evidence of biological activity. Howell will be involved in this programme. The test bed area is to be the cold desserts of Antartica. Howell brought us up-to-date with this incredibly demanding and fascinating project.

The rocks in Antartica are eroded by wind borne abrasives yet organic species can be found beneath the surface. Growth rates are unbelievably slow – carbon turnover takes 10,000 years! However, lichens can survive and in fact develop roots penetrating centimetres into the rocks. These materials give excellent Raman spectra. Further the technique can be used to identify the minerals involved [see report on British Museum meeting]. Howell Edwards concluded by briefly describing the Raman instrument currently under development for the Mars trip.

To conclude – a really interesting meeting, superb lectures and fascinating material. I can’t understand why more UK and geographically close spectroscopists don’t join the IRDG – the subscription is almost zero and the meetings are an ideal way of meeting and discussing problems with colleagues – oh and don’t forget the Christmas lunch each year! More details of the IRDG are given below and there's a link to an application form.

The Infrared and Raman Discussion Group, the IRDG, was formed in 1950. It is one of the oldest independent spectroscopy and specialist subject groups in the U.K., and as such is able to put on high quality, low registration fee meetings. Although a national organisation, the IRDG has several overseas members. It caters for all who are interested in the theory, practice and teaching of vibrational spectroscopy, in particular infrared and Raman spectroscopy. Membership is drawn from a wide cross-section of experience, expertise and interest areas. Members come from industry, government and academic institutions and spectrometer manufacturers and specialist accessory suppliers.

The IRDG normally holds a minimum of three one-day technical presentation and discussion meetings a year. These are held at varied locations around the U.K., excepting its very popular ‘traditional Xmas lunch’ meeting, which is held in London at King’s College around 13-20 December each year. Meetings feature talks by both members and non-members of the IRDG. Invited speakers from overseas are a regular feature, particularly at the December meeting, when circumstances make it economic for them to be invited. Since 1994, the IRDG has organised and sponsored approximately annually a one-day student prize award meeting; the Martin & Willis monetary prize, awarded in memory of two past long-serving chairman of the IRDG, is awarded for an oral presentation. Additional prizes are also awarded for oral and poster presentations. Student participants in this meeting do not have to be an IRDG member. Another regular feature in the IRDG calendar is a course on the ‘Interpretation of Infrared and Raman Spectra’, held at a U.K. university site.

Many activities of the Group, such as its ‘Xmas meeting’, its Martin & Willis student prize meeting, and its courses, receive regular generous support, both in monetary sponsorship and personnel time and equipment from spectrometer manufacturers and specialist accessory suppliers.

The 4-year membership fee is presently £15, with a special rate of £4 for bone fide students, unemployed and retired members. Full details of its committee, future and many past meetings, and much more may be found on the IRDG web site at http://www.irdg.org/ .

Click here to go to an Application Form, which you can print off, complete and return as applicable. 

REF: P.J.Hendra. Int.J.Vibr.Spec., [www.ijvs.com] 5, 6, 2  (2001)

3. Raman Spectroscopy in
Archaeology and Art History

British Museum,
London 20^th November 2001
The Editor

This one-day meeting was held in the British Museum, an institution famous (or infamous, depending on your viewpoint) for housing the ‘Elgin’ Marbles removed many a century ago from the Parthanon in Athens and its Round Reading Room where Karl Marx carried out his research in writing Das Kapital. The Marbles are still there, but the books have gone to the brand new British Library nearby and the Reading Room has become redundant. Sir Norman Foster, the architect of the revamped Reichstag masterminded the construction of a magnificent Education Centre in the rotunda and the meeting was held in one of its superb new lecture theatres.

My first impression was one of surprise at the number of people attending. I expected to see perhaps 30 faces, many of whom would be old friends. The friends were there, but most of the attendees, almost 120 of them were from all over Europe and many indeed from the Art World. These were enthusiastic practitioners expert in Art History, Restoration, Conservation and Archaeology.

The lecture programme was extensive and the posters many and very varied. It is quite clear that Raman is now well on its way to becoming established as a primary tool in the analysis of artefacts. Again and again lecturers stressed that since no sampling was needed and the laser power so low that no damage was done to the specimen’s surface, the method was unequally attractive to conservators and curators. But what can Raman tell us? An amazing amount. There was so much on offer that I can only report a few examples.

Professor Couprey using minute amounts of laser power examined the precious Fecamp Scriptorium dated between 990 and 1140AD. Two blue dyes were extensively used in this period based on Indigotin – an organic product and Lapis Lazuli – a mineral: similarly Minium and Vermillion in the red. By careful scanning of several images it is possible to trace the work of individual artists since it is a reasonable presumption that monks favoured their own particular painting materials. However, another manuscript from Saint Germain incorporates two different dyestuffs in one image. This cannot be explained by simple progress because the Corbic Scriptorium (XII^th Century) uses only one blue and this is based on Ultramarine. The differences in technique were unsuspected and are now areas of investigation.

We heard of several cases where forgeries have been uncovered. By simple historical methods, it is easy to produce a table defining when particular pigments or dyes became available. If Raman can identify the dyes, the detection of forgeries produced by careless or ignorant forgers can easily be revealed. So, we were shown ‘Roman’ artefacts containing the modern copper pthalocyonine dyes or even Rutile (titania) whites [the Romans used CaCO₃ , the Chinese CaSO₄].

Dr Steve Bell is interested in Chinese documents. Vast numbers were found sealed in caves and hence in good condition by the Stein Expedition of 1907. Many of these documents found their way into private collections and museums in Europe. Included was the first ever printed book (dated in the 9^th Century). Steven has used both resonance Raman and surface enhanced techniques to study the paper in these specimens. The paper is almost invariably dyed yellow and by Raman it is clear that the stain is Berberine. The trick is to adjust the laser wavelength until absorption occurs and then look for Raman bands. Steve Bell showed several examples but always against a huge and overwhelming fluorescence background, but undaunted we were shown how the problem can be eliminated – See Note 1 at the end of this report. Now Berberine was not the only dye used by the ancient Chinese. Some paper fragments show evidence of the presence of Palmatine. Where tree bark extracts have been used both Palmatine and Berberine are present together. It is quite clear that different artists used different dyes – the questions are who and why. Clearly, Raman is invaluable in this type of investigation.

Rob Withnall uses SERS, resonance SERS and resonance Raman to obtain even higher sensitivities [a very comprehensive, possibly the MOST up-to-date coverage of SERS and related techniques is available in the IJVS archive in Volume 4, Edition 2]. Dr Withnall is attempting to use his methods quantitatively – a very tricky prospect at such ultra high sensitivities but he showed us how considerable progress has been made detecting Raman signals in the 10^-7–10^-9M range. His work is not only developmental as he showed us spectra taken from the blue background (indigo) in a Tudor miniature portrait- see below.

SERRS spectra of Alcian Blue in the concentration range
1.8 x 10^-9 M to 3.6 x 10^-7 M.

Prof. Smith of the Muséum National d’Histoire Naturelle in Paris, is interested in much older artefacts – pre-Columbian axeheads. These are, of course, made of hard stone and the exact identity can tell archaeologists much about their origin, how far they have travelled and hence something of migration and trade patterns so long ago. Normally, Petromicro graphical methods and X-ray fluorescence would be used but these are very destructive.

The Pyroxene, garnet and titanite minerals all give good Raman spectra and all or some can be found together in the same sample axehead. The problem is to subtley analyse the spectra. Prof. Smith showed that within a mineral type, the untutored eye would deduce that all the spectra were essentially the same – hardly surprising – but it is possible to relate the subtle differences in frequency to the detailed composition of the mineral . [A data-base was referred to and I will attempt to identify this and include it in Spectroscopists’ Bookshelf. Editor’s Note].

Almost all of the papers at this stage of the meeting had described applications based on visible laser Spectrograph CCD instruments. Howell Edwards then introduced work based on F-T instrumentation. In these experiments, much higher laser powers are used but the exciting laser wavelength is in the near infrared (1.064µ) and as a result fluorscence is almost eliminated as a problem. Howell described experiments on Mummies exhumed by the Petry expedition to Egypt of 1906. The skeletal remains and their clothing had been seriously corroded by Natron (Na₂CO₃/NaHCO₃). Cellulose decomposes over the years through hexose ring opening but good diagnostic spectra were obtained. It was pointed out that Raman is far better than IR in this type of work because the vibrations of the numerous OH bands dominate much of the IR and also cause band broadening – not a problem in Raman scattering. Howell then showed results on a bead in the eye socket of a mummified cat. The bead proved to be cats claw, not as expected glass or amber. Why, no one has yet explained.

Mummification is not confined to Egypt. Much more recently ~1475AD ice bound mummies were interred in Greenland. No chemicals are involved so degradation in these cases is much less severe than in Egypt. Howell obviously has a ‘thing’ about mummification because he then moved on to South American mummies of around 1000AD. Spectroscopy proved that rather crude mummification had been attempted. The range of materials studied is quite remarkable with spectra from various ivories (some fake) being described. Howell Edwards is an expert on Lichens [see report on the IRDG meeting in London to follow] and he has applied his methods to lichen infestations in frescoes in the Palazzo Fornese (16^th Century) and in an ancient Spanish Church. Amazingly, and very destructively some have penetrated up to 10mm into the surface of the artwork.

The next two papers described work on pottery. Prof. Colomban of the CNRS showed data on glazes, sub-glazes and the body of ceramics. The latter are described as hard paste – Kaolin + Sand + Feldspar or soft paste – Sand + Clays + Chalk + Frit. Hard pastes are Alumina rich, soft richer in silica. Both can readily be distinguished using Raman methods. Silicate structures are specific to particular glazes and again can be distinguished.

Examples of application came thick and fast – identification of components in glazes, characterisation of the paste type from well known European factories, proof of fluorescence etc. He was asked why he thought Raman was a useful tool in his work. He replied that XRF yields elemental data only, the detailed fingerprint from Raman tends to be far more specific.

Prof. A. Zoppi of the University of Florence, continued in a similar vein but his pottery subjects were very old e.g. from the Tell Beydar site and dated around 3000B.C. His analysis was aimed at identifying both the source material in the body of the ceramics and also the glazes. He is also interested in tracing the firing techniques – for example their temperature and whether reducing or oxidizing. The analysis is detailed and agrees with the results from electron diffraction and X-ray fluorescence but as Prof. Zoppi pointed out, Raman is non-sampling and fast.

(a) Hematite Fe₂O₃ is the most stable iron compound under oxidising conditions, responsible for the colour of typical reddish sherds.

(b)Black magnetite Fe₃O₄ forms under reducing conditions and is the most important mineralogical phase found in black sherds.

(c)Diopside (CaMgSi₂O₆) is a typical "high temperature" mineral that forms (irreversibly) in a-rich clays through the transformation of primary calcite, above ~850°C. Its presence is thus an indication that at least such temperature values were reached firing the firing process.

We then moved on to artists materials. Prof. Vandenabeele from Ghent discussed artists materials and the possibility of dating and/or proving authenticity based on analysis of pigments. Raman with its non-sampling ability is ideal, the ability too to analyse under excellent spatial resolution (just a few microns) and, a new development, the use of fibre optic probes allowing the art historian to have data from large objects and/or fixed ones. Too many examples were given to list all but two are described as typical. Two ‘medieval’ miniatures have been examined – one of Solomon, the other of St. Barbara. Pigment analyses revealed BaSO₄ in the latter confirming that it is not medieval. René Magrithe produced pictures, many of which are being restored. Raman analyses is enabling art historians to follow the way his palette changed through his career. One unexpected find is that Magrithe used starch in his colours.

Prof. Robin Clark from University College in London, then spoke about his long standing work in the Raman field. Like other authors he demonstrated the value of the technique in identifying pigments and hence in some cases demonstrating that specimens were fake. One of the very unexpected results of his research were described e.g. he has found ultramarine in a Florentine ceramic glaze – showing that ultramarine can withstand 900ºC. He extended the range of pigments described by previous contributors by showing MnO₂ in pottery and Pb₂Sb₇ as a yellow pigment in an Egyptian vase. On the other hand, some pigments suffer from the atmosphere and become difficult for Raman e.g. in a 13^th Century lectionary PbCO₃ white has become coated with a layer about 1µ thick of the black PbS. Similarly basic copper carbonate (Azurite – blue/green) goes to CuS over the years.

Robin described a run in with a slippery looking gent who showed him an 'Egyptian' papyrus he planned to offer at auction and hoped it would raise two million pounds. Robin found anatase and oddly the owners never came back to collect their loot! To finish Prof. Clark described the case of the Vinland map in the library of Yale University. If genuine the map clearly demonstrates that America was known to Europeans well before Coloumbus ‘discovered’ the continent. He wants to apply his wizardry to the map.

To finish this part of the one day meeting, Prof. Gilbert of the University of Liege concentrated on green copper pigments in illuminated manuscripts. Again we heard a favourable comparison with X-ray fluorescence – the value of the Raman fingerprint was stressed. As an example Prof. Gilbert’s group have found four different types of copper sulphate. It was also shown how pigments can vary from country to country and can be identified by Raman methods and used for proving provenance.

Click here to view pdf file [Please note the file size is huge so may take a while].

Raman methods can be used in depth profiling if the sample is transparent – we were shown an example on a yellow specimen – the red laser will pass through such a material. Dr. Robinet of the British Museum then explored another area – corrosion deposits on iron and bronze artefacts. Again, a favourable comparison as made with X-ray methods. Dr. Robinet has also used infrared but finds Raman preferable for much of his work on iron objects and also on Egyptian copper bronzes. He showed spectra of surface corrosion and in cracks. Peculiarly, he sees Acetates possibility from out gassing from adjacent wood. We saw a wide range of spectra many of very high quality indeed demonstrating the formation of soaps on surfaces but one spectrum fascinated we spectroscopists – a Raman band of high intensity near u=2200cm^-1. What CAN it be due to, we all asked, but no-one came up with a suggestion.

Dr. Bouchard of the Muséum Natioanl d’ Histoire Naturelle in Paris, had the unenviable task of giving the last lecture. To my amazement, no-one had left, so Dr. Bouchard had an excellent and still enthusiastic audience. His interest in several different areas including mediaeval stained glass and rock art and corroded artefacts including coins. Mediaeval stained glass lasts well but it does deteriorate, reactions occur over very long periods between the pigments and the glasses themselves. By running Raman spectra on real samples and comparing with especially produced model mixtures the deterioration can be followed in detail. A submarine wreck contained iron ingots (as ballast to stabilise the craft?). The corroded surface contained basic iron III chlorides. Hardly surprising, but nevertheless useful. Although fluorescence proves to be a persistent problem, Prof. Bouchard emphasised the unique value of Raman Spectroscopy stressing that the information available is so detailed that the palette for stained glass artists can be developed.

In addition to the lectures, we were also able to inspect some excellent posters. I picked up, or was sent extracts from these and we have included them as pdf files.

G.Di Lonardo, F.Ospitali and F. Tullini, Università di Bologna, Italy
Danilo Bersani, Physics Department, University of Parma, Italy
[Please note the file sizes are quite big so may take a while]

To summarise – I don’t think I have attended a better meeting for years. I was bowled over by the enthusiasm and dynamism of everyone involved – the attendees, the lecturers and the organisers. From my own point of view I found it fascinating that attendees and lecturers fell into two groups: established spectroscopists who had been contacted by conservators or museum staff and Scientific conservators who had "got into" Raman spectroscopy. Both have their value but in the end the latter are the real driving force in the development of new techniques.

In many Raman spectra, the bands appear against an overwhelming background fluorescence. If a visible laser is being used, the fluorescence can be reduced by exposure to the laser, but even so fluorescence can still be a severe problem in that the bands tend to be obscured – if the fluorescence background can be reduced perhaps the Raman bands can be revealed.

1. Steve records a conventional spectrum memory.
2. He then moves the frequency scan by about ½ width of the Raman bands [This can be done on a CCD/spectrograph by tweaking the grating or in an F-T Raman instrument by changing the laser line frequency]
3. Run another spectrum.

Subtract 1 from 3. The background will essentially cancel out but the Raman lines will appear something like a first differential spectrum against a fairly flat background. Steve Bell uses ‘curve fitting’ to resurrect the spectrum, but a first differential (^dI/_du) will do the job. Although background noise will be apparent, the Raman spectrum now looks very adequate.

As a result of this wonderful meeting, I am convinced that Raman will provide a really significant input into this fascinating field, an input much more significant than sampling currently used.

After the meeting, I declined a glass of wine and hurried to the nearest Underground Station. As I reached the train level, we were informed that the station was CLOSED due to a "security event". After walking to the next station I duly missed by train home – perhaps I should have stayed for that drink!!

REF: P.J.Hendra. Int.J.Vibr.Spec., [www.ijvs.com] 5, 6, 3  (2001)

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