Letter | Published:

Measurement of the frequency of the methane-stabilised laser at 3.39 µm and of the R(32) transition of CO2 at 10.17 µm


ACCURATE, infrared, frequency and wavelength measurements now constitute the best means of determining the speed of light, and provide a link between the standards of length and time. We measured the frequency of the methane-stabilised He–Ne laser at 3.39 µm, and found good agreement with the result obtained by Evenson et al.1. The methane frequency was related to the caesium standard by using both the R(12) transition of CO2 at 9.3 µm, which has already been measured2, and the R(32) transition of CO2 at 10.17 µm.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    Evenson, K. M., Wells, J. S., Petersen, F. R., Danielson, B. L., and Day, G. W., Appl. Phys. Lett., 22, 192–195 (1973).

  2. 2

    Blaney, T. G., Bradley, C. C., Edwards, G. J., Knight, D. J. E., Woods, P. T., and Jolliffe, B. W., Nature, 244, 504 (1973).

  3. 3

    Hougen, J., J. chem. Phys., 39, 358–363 (1963).

  4. 4

    Freed, C., and Javan, A., Appl. Phys., Lett., 17, 53–56 (1970).

  5. 5

    Barger, R. L., and Hall, J. L., Phys. Rev. Lett., 22, 4–8 (1969).

  6. 6

    Terrien, J., Metrologia, 10, 9 (1974).

Download references

Author information

Rights and permissions

Reprints and Permissions

About this article

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.