Yuyan Liu

Near-infrared laser absorption spectroscopy of the CS+ cation

The (1, 0) band of the A(2)II-X(2)Sigma(+) transition of the CS+ cation has been measured in absorption at Doppler-limited resolution, between 12 400 and 13 000 cm(-1). The spectrum was recorded using differential velocity modulation detection and a Ti: sapphire laser as the near-infrared light source. The upsilon = 1 A(2)II upper state of the band is perturbed by the upsilon = 10 level of the ground state. A deperturbation analysis using > 300 rotational lines was carried out to derive accurate ground-and upper-state parameters, The ground-state rotational and fine-structure constants are in very good agreement with those from a Fourier transform emission study in which the ground-state constants were derived from combination differences

Spectroscopic analysis of asymmetric top free radicals - Application to pure rotational spectra of NO2 in the ground vibronic state

Several key problems involved in the analyses of spectra of asymmetric top molecules, i.e., the effective Hamiltonian, the representation and basis vector, identification of energy levels, the selection rules, the relative intensity, and Zeeman tuning rate, were elucidated systematically. Introducing the high-order centrifugal distortion terms into the effective Hamiltonian, the precision for calculation has been improved substantially, which allows us to analyze the high-lying rotational transitions. A global analysis of all available spectra of14N16O2 in the ground vibronic state has been made to obtain a set of molecular constants of14N16O2 in the ground vibronic state which is the most precise and extensive so far. Using the improved parameters, some FIR LMR lines left unassigned hitherto have been identified successfully.

Measurement of pressure-broadening linewidths of NO from the fitting of LMR spectra with corrections of instrumental broadening

For absorption lines, the distortion of spectral lines by experimental spectrometers must be considered in measuring linewidth which has been investigated by many authors. While in the derivative spectrum, we managed to give the corrections of instrumental broadening and distortion to obtain accurate linewidths. We developed a universal fitting program which was explored together with the method of correction in the fundamental band spectra of LMR of NO. The uncorrected halfwidths were compared with the corrected values, which were obtained from the program. The results of comparison are very satisfactory and demonstrate their useful application to analyze experimental spectra.

On the nonlinearity of the Zeeman effect of NO in the moderate field by intracavity laser magnetic resonance at 1842 cm−1

With the high sensitivity and high resolution of the techniques of intracavity laser magnetic resonance spectroscopy, strong nonlinearity of the Zeeman effect in the NO molecule has been observed in a moderate external field. A fairly simple and effective method of modelling the 2nd order Zeeman effect without recoursing to full matrix diagonalization has been developed and successfully used to analyze the nonlinearity of Zeeman effect in this Letter. Results agree well with those calculated by matrix diagonalization of precise Halmiltonian in which the off-diagonal Zeeman interaction are included

A novel differential velocity modulation laser spectroscopy

Experimental investigation of a novel differential velocity modulation laser spectroscopy is reported and demonstrated with the spectra of n2+ A2Dm -X2Óg+ Meinel system. The S/N ratio excesses 500· ·1, about 60 times higher than that with the traditional non-differential technique. With this technique, we obtained the high-resolution electronic absorption spectra of A2D-X2Ó+ (1, 0) vibration-al band of CS+ for the first time. It is confirmed that this technique will be a powerful method and receive wide application in studies of new molecular ions.