Absolute Frequency Measurement of an HDO Absorption Line near 1480 cm−1

✍ Scribed by K.J. Siemsen; J.E. Bernard; A.A. Madej; L. Marmet

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 39 KB
• Volume: 199
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.1999.8001

✦ Synopsis

A carbon monoxide laser operating on the P(15) 25-24 transition at 1480 cm Ϫ1 was used as an intermediate transfer frequency in our cesium-clockbased measurement of an optical frequency standard at 193 THz (1.556 m). The CO laser frequency was locked to the saturated absorption dip of a nearby HDO line and was simultaneously measured against the NRC H4 hydrogen maser (a cesium clock transfer standard) with help of the NRC infrared frequency chain (1). Thus, as a by-product, the absolute frequency of the HDO line was obtained. The absorption line measured belongs to the 2 band of HDO and is identified as JЈ, KЈ A , KЈ C -JЉ, K Љ A , K Љ C ϭ 5, 2, 4 -5, 1, 5 according to reference (2).

A small fraction (20 mW) of the available CO laser power (300 mW) was sent through a quartz crystal controlled acousto-optic modulator (AOM) which served as an optical isolator and frequency shifter. The AOM shifted the laser frequency by ϩ52.000 MHz into resonance with the HDO line. A telescope