Section: 9 | Spectroscopic Constants of Diatomic Molecules |
Help Manual

Page of 15
Type a page number and hit Enter.
  Back to Search Results
Type a page number and hit Enter.
Additional Information
One or more tables in this document differ to those in the book. This is due to space restrictions in the book.
Summary of table differences
The table 'Spectroscopic Constants of Diatomic Molecules' has one or more different columns to those in the book version.
How to Cite this Reference
The recommended form of citation is:
John R. Rumble, ed., CRC Handbook of Chemistry and Physics, 103rd Edition (Internet Version 2022), CRC Press/Taylor & Francis, Boca Raton, FL.
If a specific table is cited, use the format: "Physical Constants of Organic Compounds," in CRC Handbook of Chemistry and Physics, 103rd Edition (Internet Version 2022), John R. Rumble, ed., CRC Press/Taylor & Francis, Boca Raton, FL.


David R. Lide

This table lists the leading spectroscopic constants and equilibrium internuclear distance re in the ground electronic state for selected diatomic molecules. The constants are those describing the vibrational and rotational energy through the expressions:

Evib/hc = ωe(v + ½) – ωexe(v + ½)2 + •••

Erot/hc = BvJ(J + 1) – Dv[J(J + 1)]2 + •••


Bv = Beαe(v + ½) + •••

Dv = De + •••

Here v and J are the vibrational and rotational quantum numbers, respectively, h is Planck’s constant, and c is the speed of light. In this customary formulation the constants ωe , Be , etc., have dimensions of inverse length; in this table they are given in units of cm–1.

Users should note that higher order terms in the above energy expressions are required for very precise calculations. The references contain constants for many of these higher terms, as well as more precise values of the lower constants. Also, if the ground electronic state is not 1Σ, additional terms are needed to account for the interaction between electronic and pure rotational angular momentum. For some molecules in the table, the data have been analyzed in terms of the Dunham series expansion:

E/hc = ΣlmYlm(v + ½)lJ m(J + 1)m

In such cases it has been assumed that Y10 = ωe , Y01 = Be , etc., although in the highest ,approximations these identities are not precisely correct. Some of the values of re in the table have been corrected for breakdown of the Born-Oppenheimer approximation, which can affect the last decimal place. Because of differences in the method of data analysis and limitations in the model, care should be taken in comparing re values for different molecules to a precision beyond 0.001 Å. Column definitions for the table are as follows.

Column heading Definition
Mol. form. Molecular formula of diatomic molecule; molecules are listed in alphabetical order by formula as most commonly written. In most cases this form places the more electropositive element first, but there are exceptions such as OH, NH, CH, etc. 
Molecule Isotopic specification of the diatomic molecule; superscripts indicate isotope for each element of the diatomic molecule
State Spectroscopic state symbol
ωe Vibrational constant — first term, in cm-1; entries in the ωe column that are marked by * give the interval between v = 0 and v = 1 states instead of a value of ωe
ωexe Vibrational constant — second term, in cm-1
Be Rotational constant in equilibrium position, in cm-1
αe Rotational constant — first term, in cm-1
De Centrifugal distortion constant, in cm-1
re Equilibrium internuclear distance, in Å
Ref. Reference number

Refs. 1–5 are evaluated compilations covering many molecules and giving references to the original literature.


  1. Huber, K. P., and Herzberg, G., Molecular Spectra and Molecular Structure IV. Constants of Diatomic Molecules, Van Nostrand Reinhold, New York, 1979. []
  2. Landolt-Börnstein, Numerical Data and Functional Relationships in Science and Technology, New Series, II/6 (1974), II/14a (1982), II/14b (1983), II/19a (1992), II/19d-1 (1995), II/24a (1998), Molecular Constants, Springer-Verlag, Heidelberg.
  3. Lovas, F. J., and Tiemann, E., J. Phys. Chem. Ref. Data 3, 609, 1974. []
  4. Irikura, K. K., J. Phys. Chem. Ref. Data 35, 389, 2007. []
  5. Lovas, F. J., Tiemann, E., Coursey, J. S., Kotochigova, S. A., Chang, J., Olsen, K., and Dragoset, R. A., Diatomic Spectral Database (version 2.0). Available:, National Institute of Standards and Technology, Gaithersburg, MD, November 2009.
  6. Wormsbecher, R. F., Hessel, M. M., and Lovas, F. J., J. Chem. Phys. 74, 6893, 1981. []
  7. Hedderich, H. G., Dulick, M., and Bernath, P. F., J. Chem. Phys. 99, 8363, 1993. []
  8. Ram, R. S., and Bernath, P. F., J. Mol. Spectrosc. 176, 320, 1996. []
  9. Miller, C. E., and Drouin, B. J., J. Mol. Spectrosc.. 205, 312, 2001. []
  10. Tellinghuisen, P. C., Tellinghuisen, J., Coxon, J. A., Velazco, J. E., and Setser, D. W., J. Chem. Phys. 68, 5187, 1978. []
  11. Muntianu, A., Guo, B., and Bernath, P. F., J. Mol. Spectrosc. 176, 274, 1996. []
  12. Yamada, C., Chang, M. C., and Hirota, E., J. Chem. Phys. 86, 3804, 1987. []
  13. Wang, X., Magnes, J., Marjatta Lyyra, A., Ross, A. J., Martin, F., Dove, P. M., and Le Roy, R. J., J. Chem. Phys. 117, 9339, 2002. []
  14. Yamada, C., and Hirota, E., J. Chem. Phys. 99, 8489, 1993. []
  15. James, A. M., Kowalczyk, P., Fournier, R., and Simard, B., J. Chem. Phys. 99, 8504, 1993. []
  16. Campbell, J. M., Dulick, M., Klapstein, D., White, J. B., and Bernath, P. F., J. Chem. Phys. 99, 8379, 1993. []
  17. White, J. B., Dulick, M., and Bernath, P. F., J. Chem. Phys. 99, 8371, 1993. []
  18. Shayesteh, A., Appadoo, D. R. T., Gordon, I., Le Roy, R. J., and Bernath, P. F., J. Chem. Phys. 120, 10002, 2004. []
  19. Sanz, M. E., McCarthy, M. C., and Thaddeus, P., J. Chem. Phys. 119, 11715, 2003. []
  20. Müller, W., and Meyer, W., J. Chem. Phys. 80, 3311, 1984. []
  21. Staanum, P., Pashov, A., Knöckel, H., and Tiemann, E., Phys. Rev. A 75, 042513, 2007. []
  22. Lovas, F. J., Maki, A. G., and Olson, W. B., J. Mol. Spectrosc. 87, 449, 1981. []
  23. Bogey, M., Demuynck, C., and Destombes, J. L., Chem. Phys. 66, 99, 1982. []
  24. Babou, Y., Rivière, Ph., Perrin, M. Y., and Soufiani, A., Int. J. Thermophys. 30, 416, 2009. []
  25. Skatrud, D. D., DeLucia, F. C., Blake, G. A., and Sastry, K. V. L. N., J. Mol. Spectrosc. 99, 35, 1983. []
  26. Le Floch, A., Mol. Phys. 72, 133, 1991. []
  27. George, T., Urban, W., and Le Floch, A., J. Mol. Spectrosc. 165, 500, 1994. []
  28. Mürtz, P., Thümmel, H., Pfelzer, C., and Urban, W., Mol. Phys. 86, 1362, 1995.
  29. Maki, A. G., Lovas, F. J., and Suenram, R. D., J. Mol. Spectrosc. 91, 424, 1982. []
  30. Engelke, F., Ennen, G., and Meiwes, K. H., Chem. Phys. 66, 391, 1982. []
  31. Tanaka, T., Tamura, M., and Tanaka, K., J. Mol. Struct. 413, 153, 1997. []
  32. Ng, K. F., Zou, W., Liu, W., and Cheung, S.-C., J. Chem. Phys. 146, 094308, 2017. []

Spectroscopic Constants of Diatomic Molecules

Mol. form.NameCAS Reg. No.MoleculeStateωe/cm-1ωexe/cm-1Be/cm-1αe/cm-1De/10-6 cm-1re/ÅRef.
Continued on next page...
AgBrSilver(I) bromide7785-23-1107Ag79Br1Σ+249.570.630.0648330.00023610.01752.393111,2,3
AgClSilver(I) chloride7783-90-6107Ag35Cl1Σ+343.491.170.122983880.000595410.063052.280791,2,3
AgDSilver(I) hydride-d13816-78-9107Ag2H1Σ+1250.7017.173.25720.072285.91.61801,2
AgFSilver(I) fluoride7775-41-9107Ag19F1Σ+513.452.590.26570200.00192060.2841.983181,2,3
AgHSilver(I) hydride13967-01-6107Ag1H1Σ+1759.934.066.4490.2013441.6181,2
AgISilver(I) iodide7783-96-2107Ag127I1Σ+206.500.460.044868210.00014140.008472.544631,2,3
AgOSilver(II) oxide1301-96-8107Ag16O2Π1/2490.23.10.30200.00250.452.0031,2
AlBrAluminum monobromide22359-97-327Al79Br1Σ+378.01.280.159197130.000860450.112852.294811,2
AlClAluminum monochloride13595-81-827Al35Cl1Σ+481.772.100.243930070.001611080.250172.130147
AlDAluminum monohydride-d22737-86-627Al2H1Σ+1211.7715.063.31839290.069877399.421.6463717
AlFAluminum monofluoride13595-82-927Al19F1Σ+802.324.850.552480210.004984261.04641.654374,5
AlHAluminum monohydride13967-22-127Al1H1Σ+1682.3729.056.39378420.1870527368.531.6473617
AlIAluminum monoiodide29977-41-127Al127I1Σ+316.11.00.117699850.000558592.537101,2
AlOAluminum monoxide14457-64-827Al16O2Σ+979.497.010.64138560.00577961.081.617824
AlSAluminum monosulfide12251-90-027Al32S2Σ+617.113.330.28003680.00178230.222.028284
AsDArsenic monohydride-d17534-23-575As2H3Σ-1484*3.6688901.53061,2
AsHArsenic monohydride12628-08-975As1H3Σ-2130*7.30670.21173271.523151,2
AsNArsenic nitride26754-98-375As14N1Σ+1068.545.410.545510.0033660.531.61841,2
  • * Indicates a value for the interval between v = 0 and v = 1 states instead of a value of ωe.

Page 1 of 15

Entry Display
This is where the entry will be displayed

Log In - Individual User
You are not within the network of a subscribing institution.
Please sign in with an Individual User account to continue.
Note that Workspace accounts are not valid.

Confirm Log Out
Are you sure?
Log In to Your Workspace
Your personal workspace allows you to save and access your searches and bookmarks.
Remember Me
This will save a cookie on your browser

If you do not have a workspace Log In click here to create one.
Forgotten your workspace password? Click here for an e-mail reminder.
Log Out From Your Workspace
Are you sure?
Create your personal workspace
First Name (Given)
Last Name (Family)
Email address
Confirm Password

Incorrect login details
You have entered your Workspace sign in credentials instead of Individual User sign in credentials.
You must be authenticated within your organisation's network IP range in order to access your Workspace account.
Click the help icon for more information on the differences between these two accounts.
Incorrect login details
You have entered your Individual User account sign in credentials instead of Workspace credentials.
While using this network, a personal workspace account can be created to save your bookmarks and search preferences for later use.
Click the help icon for more information on the differences between Individual User accounts and Workspace accounts.
My Account

Change Your Workspace Password
Current Password

New Password
Confirm New Password

Update your Personal Workspace Details
First Name (Given)
Last Name (Family)
Email address

Workspace Log In Reminder
Please enter your username and/or your e-mail address:

Email Address

Searching for Chemicals and Properties

The CRC Handbook of Chemistry and Physics (HBCP) contains over 700 tables in over 450 documents which may be divided into several pages, all categorised into 17 major subject areas. The search on this page works by searching the content of each page individually, much like any web search. This provides a challenge if you want to search for multiple terms and those terms exist on different pages, or if you use a synonym/abbreviation that does not exist in the document.

We use metadata to avoid some of these issues by including certain keywords invisibly behind each table. Whilst this approach works well in many situations, like any web search it relies in the terms you have entered existing in the document with the same spelling, abbreviation etc.

Since chemical compounds and their properties are immutable, a single centralised database has been created from all chemical compounds throughout HBCP. This database contains every chemical compound and over 20 of the most common physical properties collated from each of the >700 tables. What's more, the properties can be searched numerically, including range searching, and you can even search by drawing a chemical structure. A complete list of every document table in which the compound occurs is listed, and are hyperlinked to the relevant document table.

The 'Search Chemicals' page can be found by clicking the flask icon in the navigation bar at the top of this page. For more detailed information on how to use the chemical search, including adding properties, saving searches, exporting search results and more, click the help icon in to top right of this page, next to the welcome login message.

Below is an example of a chemical entry, showing its structure, physical properties and document tables in which it appears.

image of an example chemical entry
We use cookies to improve your website experience. To learn about our use of cookies and how you can manage your cookie settings, please see our Cookie Policy. By continuing to use the website, you consent to our use of cookies.
Cookie Policy

Cookie Policy

We have developed this cookie policy (the “Cookie Policy”) in order to explain how we use cookies and similar technologies (together, “Cookies”) on this website (the “Website”) and to demonstrate our firm commitment to the privacy of your personal information.

The first time that you visit our Website, we notify you about our use of Cookies through a notification banner. By continuing to use the Website, you consent to our use of Cookies as described in this Cookie Policy. However, you can choose whether or not to continue accepting Cookies at any later time. Information on how to manage Cookies is set out later in this Cookie Policy.

Please note that our use of any personal information we collect about you is subject to our Privacy Policy.

What are Cookies?

Cookies are small text files containing user IDs that are automatically placed on your computer or other device by when you visit a website. The Cookies are stored by the internet browser. The browser sends the Cookies back to the website on each subsequent visit, allowing the website to recognise your computer or device. This recognition enables the website provider to observe your activity on the website, deliver a personalised, responsive service and improve the website.

Cookies can be ‘Session Cookies’ or ‘Persistent Cookies’. Session Cookies allow a website to link a series of your actions during one browser session, for example to remember the items you have added to a shopping basket. Session Cookies expire after a browser session and are therefore not stored on your computer or device afterwards. Persistent Cookies are stored on your computer or device between browser sessions and can be used when you make subsequent visits to the website, for example to remember your website preferences, such as language or font size.

Cookies We Use and Their Purpose

We use three types of Cookies - ‘Strictly Necessary’ Cookies, ‘Performance’ Cookies and ‘Functionality’ Cookies. Each type of Cookie and the purposes for which we use them are described in this section. To learn about the specific Cookies we use, please see our List of Cookies.

1. Strictly Necessary Cookies

‘Strictly Necessary’ Cookies enable you to move around the Website and use essential features. For example, if you log into the Website, we use a Cookie to keep you logged in and allow you to access restricted areas, without you having to repeatedly enter your login details. If you are registering for or purchasing a product or service, we will use Cookies to remember your information and selections, as you move through the registration or purchase process.

Strictly Necessary Cookies are necessary for our Website to provide you with a full service. If you disable them, certain essential features of the Website will not be available to you and the performance of the Website will be impeded.

2. Performance Cookies

‘Performance’ Cookies collect information about how you use our Website, for example which pages you visit and if you experience any errors. These Cookies don’t collect any information that could identify you – all the information collected is anonymous. We may use these Cookies to help us understand how you use the Website and assess how well the Website performs and how it could be improved.

3. Functionality Cookies

‘Functionality’ Cookies enable a website to provide you with specific services or a customised experience. We may use these Cookies to provide you with services such as watching a video or adding user comments. We may also use such Cookies to remember changes you make to your settings or preferences (for example, changes to text size or your choice of language or region) or offer you time-saving or personalised features.

You can control whether or not Functionality Cookies are used, but disabling them may mean we are unable to provide you with some services or features of the Website.

First and Third Party Cookies

The Cookies placed on your computer or device include ‘First Party’ Cookies, meaning Cookies that are placed there by us, or by third party service providers acting on our behalf. Where such Cookies are being managed by third parties, we only allow the third parties to use the Cookies for our purposes, as described in this Cookie Policy, and not for their own purposes.

The Cookies placed on your computer or device may also include ‘Third Party’ Cookies, meaning Cookies that are placed there by third parties. These Cookies may include third party advertisers who display adverts on our Website and/or social network providers who provide ‘like’ or ‘share’ capabilities (see the above section on Targeting or Advertising Cookies). They may also include third parties who provide video content which is embedded on our Website (such as YouTube). Please see the website terms and policies of these third parties for further information on their use of Cookies.

To learn about the specific First Party and Third Party Cookies used by our, please see our List of Cookies.

Managing Cookies

You always have a choice over whether or not to accept Cookies. When you first visit the Website and we notify you about our use of Cookies, you can choose not to consent to such use. If you continue to use the Website, you are consenting to our use of Cookies for the time being. However, you can choose not to continue accepting Cookies at any later time. In this section, we describe ways to manage Cookies, including how to disable them.

You can manage Cookies through the settings of your internet browser. You can choose to block or restrict Cookies from being placed on your computer or device. You can also review periodically review the Cookies that have been placed there and disable some or all of them.

You can learn more about how to manage Cookies on the following websites: and

Please be aware that if you choose not to accept certain Cookies, it may mean we are unable to provide you with some services or features of the Website.

Changes to Cookie Policy

In order to keep up with changing legislation and best practice, we may revise this Cookie Policy at any time without notice by posting a revised version on this Website. Please check back periodically so that you are aware of any changes.

Questions or Concerns

If you have any questions or concerns about this Cookie Policy or our use of Cookies on the Website, please contact us by email to [email protected]

You can also contact the Privacy Officer for the Informa PLC group at [email protected].

Our Cookies

Here is a list of cookies we have defined as 'Strictly Necessary':

Taylor and Francis 'First Party' Cookies


















Here is a list of the cookies we have defined as 'Performance'.

'Third Party' Cookies

Google Analytics:





The Voluntary Product Accessibility Template (VPAT) is a self-assessment document which discloses how accessible Information and Communication Technology products are in accordance with global standards.

The VPAT disclosure templates do not guarantee product accessibility but provide transparency around the product(s) and enables direction when accessing accessibility requirements.

Taylor & Francis has chosen to complete the International version of VPAT which encompasses Section 508 (US), EN 301 549 (EU) and WCAG2.1 (Web Content Accessibility Guidelines) for its products.

Click here for more information about how to use this web application using the keyboard.

This is replaced with text from the script
This is replaced with text from the script
Top Notification Bar Dialog Header
Your Session is about to Expire!
Your session will expire in seconds

Please move your cursor to continue.