A tunable laser at λ=3.39 μm with line width of 7 Hz used in investigating a hyperfine structure of theF 2 (2) line of methane

A laser spectrometer is described which was used in exploring resonance shapes of about 1000 Hz width in methane in the region of low absorption of about 10⁻⁶ cm⁻¹. We report on first measurements of relative intensities of hyperfine components of theF ₂ ⁽²⁾ line in methane, on direct observations of line splitting due to a recoil effect and of a non-linear dependence of collisional broadening of resonances in the transit region, and on observation of an anomalous Zeeman effect in hyperfine components in a longitudinal magnetic field. The results of this work were summarized by one of the authors (V.C.) at the 2nd Symposium on Frequency Standards and Metrology (Boulder, Colo., USA, July 1976) and at lectures in the School Enrico Fermi (Varenna, Italy, July 1976).