No abstract

Using multi reference configuration interaction (MRCI) method, with aug-cc-pV5Z, aug-cc-pv6z, aug-cc-pcv5z, aug-cc-pcv6z basis sets etc., the single point energy of the ground state and the first excited state and second excited state of C-2are calculated. Then LEVEL program is used to fit out the spectroscopic constants of three states. Results obtained by MRCI/aug-cc-pcv5z-dk method are close to the experimental values.

We study the absorption spectra of water vapor by the 899-29 Ti:sapphire laser in the region between 12 252-12 312 cm-1. Due to the weak absorption of H2O, a folded multi-pass optical path cell of Herriott-type is used to increase the sensitivity of detection. Totally, forty-three lines with intensity ranging around 10-24cm-1/molecule are recorded and the centre frequency of transitions is derived by fitting observed lines using Voigt profile.

Due to the weak absorption of H2O in the near infra red region, the frequency modulation (FM) is one of good technologies to increase the sensitivity of detection. This method is used to study the absorption spectra of water-vapor in the region around 814.65 nm. Compared to direct absorption method, the signal-to-noise of spectral signal is enhanced. Therefore, the laser FM is a good potential spectroscopic technology in the application of laser sensor for trace gas.