1. Introduction and summary

Herewith we would like to introduce the project of a new literature database - we call it the Photochemistry Database (PCDB) - accessible on the internet, and intended to cover photochemistry and related fields, such as organic and bioorganic optical spectroscopy, molecular aspects of photobiology and radiation biology, and radiation chemistry.

This database will include the following features which hopefully should make it a useful tool for the scientist:

- A broad coverage of journals and topics. Reasonable completeness is aimed at in the fields listed above, but items from neighboring areas are also included.

- Regular updating and browsing of latest entries. Authors' affiliations and e-mail addresses (if available) will be supplied.

- An efficient searching engine. This includes use of fast software and implementation of a new and flexible searching system.

The database in its actual form starts with the year 1996. Entries from earlier years will also be provided although on a narrower basis.

2. Aim and scope

Today's broad availability of the internet offers new opportunities for scientific information distribution and retrieval. The creation of discipline-specific searchable literature databases should make the search for literature quicker and easier. We are presenting here a new literature database centered on the discipline of photochemistry but covering several other fields too, as will be detailed below. This Photochemistry Database is now available freely. Its future availability is still a matter of discussions and will be made known on the webpage in due time.

Here is a short (maybe incomplete) list of criteria a «really useful» literature database should conform to:

- It should be accessible at any time and without having to wait too long for access and response. This means that one would like to access it from one own's PC. And one would like to be able to access as often as one wishes.

- It should be able to respond to search queries in a flexible yet efficient way. Questions concerning literature may be very varied: you might be interested in knowing properties of a specific compound, or in retrieving review articles in a broad field.

- Consequently, you would wish your database to be specific to your discipline - that is, reasonably complete - but not too narrowly so.

- Recent entries to the database should be provided for browsing. Authors' affiliations and - since this is an internet venture - also e-mail addresses should be known.

- Information should - of course - be as detailed as possible. For obvious reasons, a database on the web will not be able to provide as much information as, say, the Chemical Abstracts. But even if immediate access to the abstract is not possible keyword entries can provide some information.

We have tried - and are still trying - to make the Photochemistry Database conform to these expectations. As already mentioned in the introduction, the database is centered on the fields of photochemistry, organic and bioorganic optical spectroscopy, and molecular aspects of photobiology. In the past years, these fields have had a tremendous impact on new scientific developments in other areas, such as atmospheric chemistry, nonlinear optics, materials science, or medical diagnosis and therapy, to name a few. We are trying to keep track of these developments.

One thing that will not be possible, or at least not satisfactorily so, is searching «back in time» before the year 1996. Some data of earlier years will be provided, but coverage will be unreliable. This is so because the Photochemistry Database grew out of a private venture which was not intended to be publicized until implementation on the internet could be envisaged.

3. Searching

Searching for keywords can be a tricky business. Really precise keyword searching requires utilization - both by the database provider and the database user - of a keyword thesaurus which in order to be useful necessarily has to be voluminous. Keyword allocation then obviously is time-consuming and therefore expensive. For the Photochemistry Database, we have tried to steer a middle course by devising what we call a hierarchical code system of topics. This consists in dividing the whole field covered by the database in subfields, each with further subdivisions. The number code allocated to each subdivision then may be simply used as a keyword on the same level with, say, the name of a chemical compound. In the following, we list the 29 main subfields; at the same time, this will give an idea of the scope of the Photochemistry Database.

01. Studies of structure (either of systems of importance with respect to photochemistry, or by use of spectroscopic techniques such as fluorescence).
02. Studies of motion
03. Reaction kinetics in condensed phases, diffusion-controlled reactions
04. Recombination processes
05. Spin dynamics
06. Nonlinear optical properties of molecules
07. Excited states and spectroscopy
08. Energy and electron transfer
09. Proton and hydrogen transfer
10. Dynamics of photoreactions
11. Photoionization
12. Excitons and excess electrons
13. Reaction intermediates
14. Interactions between radiation and matter
15. Radiation chemistry - mechanistic and product studies
16. Photochemistry - mechanistic and product studies
17. Supramolecular systems - photophysics and photochemistry
18. Polymers
19. Photosensitization, photocatalysis, photoelectrochemistry
20. Photophysics and photochemistry on surfaces
21. Environmental studies
22. Sonochemistry and sonoluminescence
23. Oxidation and antioxidants
24. Radiation biology
25. Photobiology
26. Technical applications
27. Measuring techniques
28. Reviews
29. Educational

Most of these subfields are further subdivided. We won't give the complete list here - it can be downloaded from the website - but cite just an example from the field «07.»

«07.2.» stands for «spectroscopy and radiative deactivation»

«07.2.2.» stands for «experimental studies»

«07.2.2.D» stands for «benzene derivatives».

This means that for searching purposes the string «07.2.2.D» can be used as a keyword to retrieve publications on experimental studies in spectroscopy or photophysics of benzene derivatives. This keyword might be combined with a second one, e.g. one of the experimental technique acronyms (which will be introduced below) such as «FSP» for fluorescence spectroscopy. Alternatively, a less specific search can be made by using one of the strings which are higher in the hierarchy: «07.2.2.», «07.2.», or «07.», and combining it with another keyword such as the name of a chemical compound. Care must be taken to choose keyword combinations which are specific enough not to yield a prohibitively large number of hits; for instance there are 247 entries alone for the subfield «07.2.2.D» in 1996! Therefore, combination of a given number code with a second keyword is usually mandatory. Two keywords are allowed in the persent version; this will be increased to three in the future.

As can be seen from the subfield list, review articles are treated as an own subfield (28). As stated above, this may be combined with another keyword («fullerene», to take an example), but it may also be prefixed to any number code to retrieve the review articles pertaining to the chosen subfield; for example: «28.07.2.2.» for: review articles on experimental studies in spectroscopy and radiative deactivation.

We now turn to another searching feature of the Photochemistry Database, the acronyms for experimental techniques. Whenever the information is available when a database record is generated, the main experimental techniques used are added to the keywords in the form of acronyms; the list of acronyms used can also be downloaded from the webpage. Again, these acronyms can be combined with other keywords including the number codes (an example has been given above).

4. Implementation

Producing and distributing such a database is not terribly cost-intensive, but unfortunately not for nothing. We are now trying to find ways to solve this problem.

We would like to invite all colleagues to make use of the current version at http://pchem.ttk.mta.hu/. The future of this database will of course very much depend on the way it is used and accepted by the community. We would therefore like to invite comments, criticism and encouragment at the e-mail addresses listed below.

For the database:

Gottfried Grabner

For software and webpage:

Zsolt Kúti