J. S. Wells

Accurate frequencies of molecular transitions used in laser stabilization: the 3.39‐μm transition in CH4 and the 9.33‐ and 10.18‐μm transitions in CO2

The frequencies of three lasers stabilized to molecular absorptions were measured with an infrared‐frequency synthesis chain extending upwards from the cesium frequency standard. The measured values are 29.442 483 315 (25) THz for the 10.18‐μm R(30) transition in CO2, 32.134 266 891 (24) THz for the 9.33‐μm R(10) transition in CO2, and 88.376 181 627 (50) THz for the 3.39‐μm P(7) transition in CH4. The frequency of methane, when multiplied by the measured wavelength reported in the following letter, yields 299 792 456.2(1.1) m/sec for the speed of light.

Heterodyne frequency measurements on the 11.6-μm band of OCS: new frequency/wavelength calibration tables for 11.6- and 5.8-μm OCS bands

Heterodyne difference frequency measurements between a (13)CO(2) laser and a diode laser tuned (and in most cases locked) to the peaks of OCS absorption lines have been used to improve frequency calibration tables in the 860-cm(-1) region by factors of 20-50. Measurements have been made on the vibrational transitions 10(0)0-00(0)0, 11(1)0-01(1)0, and 20(0)0-10(0)0 for OCS. The measurements on the 10(0)0-00(0)0 and 20(0)0-10(0)0 transitions are also used to provide frequency calibration tables for the 20(0)0-00(0)0 band of OCS near 1700 cm(-1).

ABSOLUTE FREQUENCY MEASUREMENTS OF THE 28‐ AND 78‐μm cw WATER VAPOR LASER LINES

The two highest frequency measurements as yet reported are described. Frequencies of the 28‐ and 78‐μm cw water vapor laser lines were found to be 10.718073±0.000002 THz and 3.821775±0.000003 THz, respectively, by beating each of these radiations with the 337‐ and 373‐μm (0.89‐ and 0.80‐THz) radiation from an HCN laser, in a metal‐on‐metal point‐contact diode. The frequencies of the HCN laser were in turn measured by beating the 337‐μm radiation with 74‐GHz radiation and by measuring the 337‐ and 373‐μm frequency difference.

Extension of Absolute Frequency Measurements to the cw He–Ne Laser at 88 THz (3.39 μ)

The highest absolute frequency measurement yet reported is described. The frequency of the 3.39‐μ line from a He–Ne laser oscillating at the methane absorption frequency was found to be 88.376245 (55) THz. The frequency was measured by beating the 88‐THz radiation with the R(30) line from a cw CO2 laser and a 48‐GHz klystron in a tungsten‐on‐nickel point‐contact diode. The speed of light calculated from this frequency and previous wave‐length measurements is in agreement with the accepted value and of comparable accuracy.

ABSOLUTE FREQUENCY MEASUREMENTS OF THE CO2 cw LASER AT 28 THz (10.6μm)

The two highest cw absolute frequency measurements as yet reported are described. Frequencies of the P(18) and P(20) 10.6‐μm lines from a cwCO2 laser were found to be 28.359800 THz and 28.306251 THz±0.000025 THz, respectively. The frequencies were measured by beating each of these lines with 3.8‐THz (78μm) and 10.7‐THz (28μm) radiation from a water vapor laser and a 26‐ to 28‐GHz klystron in a tungsten‐on‐nickel point contact diode.

Heterodyne frequency measurements (at 11.6 μm) on isotopic species of carbonyl sulfide, OC34S, O13CS, OC33S, 18OCS, and O13C34S

Abstract Heterodyne frequency measurements between a frequency-stabilized 13 CO 2 reference laser and a tunable diode laser (either tuned or locked to various carbonyl sulfide absorption peaks) have been made on a number of 10 0 0-00 0 0 band transitions in the isotopic species of carbonyl sulfide: OC 34 S, O 13 CS, OC 33 S, 18 OCS, and O 13 C 34 S. These OCS frequency measurements have been combined with existing microwave data and new sets of molecular constants obtained. These constants will be used later to form part of a frequency calibration compendium based on OCS.

Heterodyne frequency measurements of 13 CO 2 laser hot band transitions

The frequencies of twenty-eight lines in the P-branch of the 01(1)1-[11(1)0,03(1)0](I) band of (13)C(16)O(2), observed in laser emission, and three lines in the R-branch, observed in absorption with a diode laser, have been carefully measured with stabilized CO(2) lasers. A significant improvement in the ro-vibrational constants has been obtained from a least squares fit to these data. The laser lines stabilized by saturated absorption techniques provide convenient, accurate (uncertainty <0.1 MHz) frequency references near 11.7 microm.

A New LEPR Spectrometer

A new spectrometer for conducting laser electron paramagnetic resonance experiments on gases is described. This spectrometer yields at least an order of magnitude better sensitivity than the first spectrometer used in this type of investigation.

Role of infrared frequency synthesis in metrology

Infrared frequency synthesis (IFS) techniques are briefly surveyed, and some important results are summarized. The recent measurement of the frequency of the methane-stabilized He-Ne laser is significant due to the accurate measurement of the methane wavelength and its fundamental role in metrology. The possibilities of an improved value for the speed of light and of additional applications for frequency measurements at various levels of accuracy are discussed.