Jieli Lin

Simple empirical analytical approximation to the Voigt profile

A simple empirical analytical approximation to the Voigt profile is proposed as a weighted sum of Lorentzian and Gaussian functions. It is prevalent in the analysis of complicated experimental spectra such as that with multibroadening mechanisms and congested or overlapped lines. The maximum errors of width, area, and peak relative to those from direct convolution of the Voigt profile are 0.01%, 0.2%, and 0.55%, respectively. The relative width error of the present approximation is smaller and its convergence of absolute strength calculation, i.e. the area under the profile, faster than for the other methods that we considered, such as Gautsch’s algorithm, which is developed by introduction of a complex probability function.

Measurement of the electric dipole moment of NO (X-2 Pi upsilon=0,1) by mid-infrared laser magnetic resonance spectroscopy

A pair of parallel Stark plates are added to a CO laser magnetic resonance spectrometer to apply electric field in the absorption cell. This apparatus is used to measure the molecular electric dipole moment via Zeeman and Stark effects simultaneously. The saturated absorption spectra of NO (X2Π3/2, ν = 1 ← 0) was observed and the electric dipole moments of NO were directly measured in the presence of an electric field. The dipole moments are determined as μ0(ν = 0) = 0.1595(15) D, μ1 (ν = 1) = 0.1425(16) D. The electric dipole moment of the vibrationally excited state (ν = 1) is determined for the first time. The dependence of the electric dipole moments on its nuclear distances is interpreted.

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.