Laser Stark spectroscopy of carbon dioxide in a molecular beam

Abstract

Laser Stark spectroscopy has been performed for CO 2 molecules in a bolometrically detected supersonic beam, using a tunable infrared F-center laser to excite rovibrational transitions in the 3715-cm −1 “ ν 1 + ν 3” band of 12C 16O 2. The very weak Stark effect of CO 2 is amply resolved by realizing an effective spectroscopic linewidth of 2 MHz and by using uniform electric field strengths in excess of 200 kV cm −1. Stark spectra for the R(0) and P(2) transitions enable evaluation of the isotropic part ( α n ) and anisotropy (Δ α n ) of the static molecular polarizability in both excited ( n = v) and ground ( n = 0) vibrational states. Direct observables are Δα v Δα 0 = 1.021(8) ; (α v - α 0) Δα v = 0.012(6) ; Δα v = 2.65(18) A ̊ 3 , the last result being 12% greater than predicted. The results test the relative magnitudes of electronic and vibrational contributions to the static polarizability and indicate the way in which the polarizability tensor varies from one vibrational state to another.