GENERAL INFORMATION FOR CONTRIBUTORS
(Revised January 1997)

Information about this journal and other APS journals is available electronically via ftp to aps.org in the subdirectories /jrnls, /pacs, revtex, etc., of the /pub directory. Most filenames include as an extension a suffix (beginning with a period), which indicates the nature of the file: .asc (plain ASCII), .pdf (portable document file, usable with Acrobat), .ps (PostScript), or .tex (TeX). Most files exist in two or three versions, distinguished by the suffix. Some specific files are cited where pertinent below. On the World Wide Web the APS research-journals server (whose URL is http://publish.aps.org/) also provides access to this material, and other information.

Manuscripts may be submitted by a variety of electronic modes (including via e-print servers, direct Web upload, and e-mail), or by conventional mail, but not by fax. Interactive submission forms, available on our Web server, are an integral part of the submission process for the e-print and Web modes, and are strongly recommended for e-mail and conventional-mail submission. These forms aid authors in supplying all the information needed in a structured format which furthers efficient procesing; they also provide a location for additional ``free form'' information. [For authors without Web browsers which support forms, noninteractive versions of the submission forms are available via ftp to aps.org in the /pub/jrnls directory as the sub_prb files (include filename suffix .asc, .tex, or .ps), or by request to the Editorial Office.]

Please specify the author to whom correspondence should be addressed, and give all available communications information for this individual (postal and e-mail addresses, phone and fax numbers), since in various circumstances they may all be useful. Please specify journal and section to which the paper is submitted, and give PACS (Physics and Astronomy Classification Scheme) index categories if possible. (The scheme is available via ftp to aps.org as the file pacs_96.asc in the /pub/pacs directory; the alphabetical index to PACS is available as the file index_96.asc in the /pub/pacs directory. Printed copies of PACS are available on request from the Editorial Office.) If an important subject of your paper cannot be appropriately classified in the PACS scheme, please give an appropritate keyword or phrase, and indicate approximately where in the scheme this topic would be best placed.

A signed APS copyright-transfer form (available in plain text, PostScript, or TeX format here) should be included with the submission, and will be required before publication. While the transfer of copyright takes effect only upon acceptance of the paper for publication in an APS journal, supplying the form initially can prevent unnecessary delays. The form appears at the end of the 18 November 1996 issue of Physical Review Letters and is available from the Editorial Office, on the World Wide Web via the URL http://publish.aps.org/ or via ftp to aps.org in the /pub/jrnls directory as the copy_trnsfrfiles (include filenames suffix .asc, .ps, or .tex). Be sure to use the latest (3/94 or later) version of the form.

Manuscripts and figures are not routinely returned to authors. Authors should indicate (preferably on initial submittal) if they want the manuscript and/or figures returned when correspondence is sent during the editorial process, and/or after a final decision has been made.

Manuscripts sent by conventional mail should be submitted in triplicate to the Editors, Physical Review, 1 Research Road, Box 9000, Ridge, NY 11961-9000. The manuscript, including the abstract, references, and captions, should be neatly printed in English, on good letter-size (e.g., in. or A4) white paper with ample margins. (The first copy, used for production purposes if the paper is accepted for publication, must be printed on one side of the paper only; additional copies, used for review purposes, may be printed on both sides of the paper.) The type size and line spacing should be sufficient to accommodate editorial markings and should be legible to our keyboarders (no more than three lines per inch and no more than 88 characters per 6 inches). It should be carefully proofread by the author. Poor reproductions are unacceptable, as are unclear or excessive handwritten insertions. For general format and style consult recent issues of this journal and the Physical Review Style and Notation Guide, available via ftp to publish.aps.org in the /pub/jrnls directory as the style_guidefiles (include filename suffix .pdf, .ps, or .tex). Additional style guidelines can be found in the Fourth Edition of the AIP Style Manual, which may be obtained for $10.00 (prepaid) from the American Institute of Physics, c/o AIDC, 64 Depot Road, Colchester, VT 05546, telephone: 800-488-2665.

Electronic submissions may be formatted in REVTeX (preferred), LaTeX, Harvmac, or Plain TeX. The file must be in ASCII containing no control codes, with line lengths of 80 characters or less. All textual material of the paper (including tables, captions, etc.) should be in electronic form, as a single file. The file should produce double-spaced output.

For information about submission via e-print servers or direct Web upload, see our Web server.

Electronic-mail submissions (and inquiries about them) should be sent to the Internet address prXtex@aps.org (where X=a, b, c, d, e, or l designates the intended journal). For the initial submission, use as the subject ``submit'' followed by the three-letter abbreviation for the name of the first author; for example, ``submit pra jones'' or ``submit PRA Jones.'' Include the filled-out submission form (or the equivalent information, including journal, section, postal address, etc.) in the first part of the electronic-mail message. Receipt of an electronic-mail submission will be acknowledged within 24 hours. Copies of the manuscript should not be sent by regular mail (only original figures) unless the electronic transmission has not been successful.

Editorial processing of an electronic mail submission cannot begin until at least review-quality copies of the figures are received. Electronic-mail transmission (one figure per file) of PostScript-formatted figures will normally meet this need. Use as the subject ``submit'' followed by the three-letter abbreviation for the name of the journal (pra, prb, prc, prd, pre, or prl), the last name of the first author, and the figure number; for example, ``submit pra jones fig 1'' or ``submit PRA Jones Fig 1.'' Alternatively, you could send scanner-reproducible journal-quality ``originals'' immediately by overnight mail to the Editorial Office. A third possibility is to send review-quality figures by fax (516-591-4141), while the ``originals'' are sent by conventional or overnight mail as soon as possible; please mark the fax transmission as being part of an electronic-mail submission.

Compuscripts are author-supplied computer files that can be used for production essentially as supplied. (Some minor style modifications may be made if needed.) If the paper is accepted for publication, the file is converted to SGML format and coding, from which base the journal pages are composed. Authors should indicate with their intial submission that they are interested in publishing in this mode. Appropriate REVTeX files are elgible. Questions about file elgibility should be directed to prXtex@aps.org (X = a, b, c, d, e, or l). Papers intended for the compuscript production program should be submitted and resubmitted by electronic mail or by DOS-formatted floppy disk.

REVTeX is APS's LaTeX macro package used to produce compuscript files with the standard structure and coding needed for our journals. The REVTeX software (macros, examples, and documentation) are available via ftp to aps.org in the /pub/revtex directory. For further information on REVTeX, inquire by electronic mail to mis@aps.org (Internet).

An information and instruction booklet regarding electronic submissions and compuscripts is available via ftp to aps.org in the /pub/jrnls/ directory as the compu_inform_pr files (include filename suffix .asc, .ps, or .tex).

When a manuscript is resubmitted, please include a summary of changes made and a brief response to all recommendations and criticisms. (Submission forms are not yet available for resubmissions; nor are the e-print and Web upload submission methods.) If the resubmission is by conventional mail, please send three copies of a complete modified manuscript; if changes are few, you may alternatively send three copies of those pages on which changes have been made (no more than three or four pages), but make sure that the page breaks are the same as in the initial manuscript. If the resubmission is by electronic mail, please send the complete file for the text if there have been any changes. (The response to the referee should be included as the first part of the electronic-mail message which contains the modified manuscript. Use as the subject of the message ``resub'' followed by the manuscript code number and the last name of the first author; for example, ``resub BC1234 Smith'' or ``resub bc1234 smith''.) For any resubmission, please state whether or not the figures have been modified, and supply new scanner-reproducible figures if there have been such changes.

The title should be concise but informative enough to facilitate information retrieval. The abstract should be self-contained (contain no footnotes). It should be adequate as an index (giving all subjects, major and minor, about which new information is given) and as a summary (giving the conclusions and all results of general interest in the article). It should be about 5%of the length of the article, but less than 500 words.

Notation should be clear, compact, and consistent with standard usage. Each symbol must be individually legible. Equations should be neatly typed or written in ink, punctuated and aligned to bring out their structure, and numbered on the right. (a) Diacritical marks (tildes, etc.) can be put over any symbol, including indices, but not over groups of symbols. (b) Three-vectors will be set in roman boldface type and should be marked in the manuscript with either a black wiggly underline or an arrow over the character. More general vectors, matrices, etc., are usually set in lightface italic type, although boldface may alternatively be used. (c) Any numerical fraction can be put on one line, e.g., . Use that form rather than , and never use , unless you mean . The solidus should be used instead of built-up fractions in running text.

Marking of mathematical material: All unusual and handwritten symbols whose identity is not obvious should be identified in the margin the first time they appear, and thereafter only if an ambiguity is still possible. For example, when necessary, identify Greek letters (not including sum and product signs) and script letters; underline italic in black; underline in black three times for capital. Identify nonalphabetic symbols by their number in the AIP Style Manual. Superscripts are normally set directly over subscripts; authors should note where readability or the meaning requires a special order by specifically marking such cases (enclose superscripts in a black-penciled inverted caret; subscripts, in a black-penciled caret). Excessive marking should be avoided.

Footnotes, including both references and comments, must be numbered consecutively in order of first appearance in the text, and should be given in a separate double-spaced list at the end of the text material. References within tables should be designated by lower-case letter superscripts and given at the end of the table. For the proper form, see the Physical Review Style and Notation Guide and recent issues of this journal. The names of all authors of works cited should be given in the references, unless the number of authors is greater than three; in this case, the first author's name followed by et al. is allowed. When reference is made to internal reports or other items not available in the open literature, it is listed as unpublished. References to classified reports or other documents with restricted circulation should be avoided. It is important to confirm the accuracy of bibliographic information in references. This becomes more important when the journal is online; establishing hyperlinks from reference lists to bibliographic and document databases depends on the accuracy of the data contained in the anchor references. Footnotes to an author's name or address should be limited to those necessary for location of the author. Electronic addresses (e.g., Internet, FAX) can be listed as footnotes. All information concerning research support should appear in the acknowledgments.

Separate tables (numbered in the order of their first appearance) should be used for all but the simplest tabular material; they must have captions, which should make the tables intelligible without reference to the text. The structure should be clear, with simple column headings giving all units.

The decision on whether results should be published in long tables depends on the precision of the data, i.e., whether they can be read accurately enough from a figure, and on how many readers are likely to use the numbers relative to the sapce needed in the journal. If additional numerical data can be obtained from a data center, from the author, or from another source either as tables or on tape, indicate how and in what format they can be obtained.

Figures should be planned for the column width of the Physical Review (approximately 8.6 cm, or in.). In some cases where the figures contain a great deal of detail, or 2 columns may be used. Wasted space at the top and bottom should be avoided. Carefully prepared figures, suitable for digital scanning, are required (original India-ink drawings or glossy prints; computer-generated figures, if of sufficient quality, are acceptable). Figures must have a clear background and unbroken lines with as much black-white contrast as possible. Final-journal-size originals or prints are preferable to oversized originals. Avoid small open symbols which tend to fill in upon reproduction, small dots and decimal points, and shading or cross-hatching that is not coarse enough to withstand reproduction. The lettering and plotted points on the figures should be large and clear enough that they will be legible on the journal pages (final journal size of lettering should be at least 2 mm). Inconsistently large or too heavy lettering should be avoided. Line weights should be consistent throughout a figure, with a final line weight of at least 0.18 mm (0.5 point). Figures reproduced directly from an automatic plotter or computer printer must have lettering of the correct size and style (e.g., MeV instead of MEV, unslashed zeros) and curves that are smooth and of sufficient line weight to allow suitable reproduction. The resolution of the drawing software and the output device should be set as high as possible (preferably 600 dpi or higher). Very fine lines in laser-generated illustrations will disappear under scanning. Photographs of apparatus are unacceptable and should be replaced by good schematic diagrams.

Photographic (continuous tone) material is screened (``halftoned'') within our production process. Avoid submitting prescreened prints of photographic material; reproduction of such figures is then seldom satisfactory. There is a risk of moiré patterns appearing in the final product. Laser-printer renditions of continuous-tone data are similarly problematic, since they are effectively prescreened. Please submit figures electronically as PostScript files (one image per file). There are greater possibilities for successful reproduction in the journal when these data are processed directly rather than via scanning of hard-copy renditions. Alternatively, supply glossy or matte-finish photographs instead, if available. Otherwise, choose the highest resolution possible and laser print the figure at its final published size.

Figures should be numbered in the order in which they are cited in the text. The original figures, as well as the copies supplied for review purposes, should be identified on the front (well outside the image area) by the number, the name of the first author, and the journal. An indication, e.g., ``TOP,'' of the intended orientation of a figure is helpful, especially in ambiguous cases. Be advised that the scanner reproduces all flaws (e.g., correction fluid, tape, smudges, writing on the back of the figure). Each figure must have its own caption; list captions on a separate sheet. Groups of figures that share a common (single) caption must be labeled ``(a), (b), (c),'' etc. It is preferable that all parts of a figure be submitted as a single piece. The figure should have properly labeled axes with correctly abbreviated units. Use the form , not . For complete instructions see the Physical Review Style and Notation Guide and the AIP Style Manual.

Some figures might be more effective in color. This option is available; price schedules can be obtained from the Editorial Office at Ridge. The cost of publishing illustrations in color must be borne in full by the respective authors and their institutions. Authors who wish to avail themselves of this option should provide 35-mm slides or transparancies, or high-quality glossy prints, which should be close to the final size expected for publication. (Negatives are not acceptable.) Polaroid color prints should be avoided. Artwork must be flexible. If submitting slides, please note that they will be removed from their jackets for the color separator. In some cases, printing requirements will prevent figures from being located in the most preferred position. To alert readers of monochrome reproductions of the article that the archive figure is in color, begin the caption with ``(Color).'' Be advised that production of an editorially accepted paper that contains color can begin only after a properly completed color-illustration authorization form has been received from the author.

The detail in some figures (continuous-tone photographs or color figures, for example) is lost on photocopying. Therefore, duplicate sets of the originals of such figures must be attached to each copy of the manuscript.

In order to reproduce figures, tables, etc., from another journal, authors must show that they have complied with the requirements of the publisher of the other journal, possibly including written agreement of both publisher and author of the originally published work. (If the original journal is published by APS, only the written agreement of the original author is required to reproduce a few figures or tables.)