Chuanxi Duan

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.

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

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.

Rotational spectrum of HCBr produced by 193-nm laser photolysis of bromoform

The pure rotational spectrum of bromomethylene (HCBr) was studied by kinetic microwave spectroscopy between 420 and 472 GHz. The HCBr radical was produced by 193-nm ArF laser photolysis of bromoform (CHBr3). More than 130 rotational transitions for both (HCBr)-Br-79 and (HCBr)-Br-81 species in the ground vibrational state were measured involving 1 less than or equal to J less than or equal to 33 and 0 less than or equal to K-a less than or equal to 5. The spectra were well described by an S-reduced Watson Hamiltonian in the I-r representation including the nuclear quadrupole and spin-rotation hyperfine terms. Rotational, centrifugal distortion, Br-79,Br-81 nuclear quadrupole and spin-rotation coupling constants were derived for both (HCBr)-Br-79 and (HCBr)-Br-81 species in the ground vibrational state

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.

Band (5, 0) in the Red System A2ΠI - X2Σ+ of CN Studied by Optical Heterodyne Magnetic Rotation Enhanced Concentration Modulation Spectroscopy

We study the CN radical using optical heterodyne magnetic rotation enhanced concentration modulation spectroscopy in the visible region. The radical has been produced in the ac glow discharge of acetonitrile with helium as the carrier gas. The (5, 0) band of the red system A(2)Pi(I) - X(2)Sigma(+) in the range 17450-17830cm(-1) has been observed and rotationally analysed. We determine a set of precise molecular constants for the v = 5 vibrational level of CN in the A(2)Pi(I) state.

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.

Assignment of Infrared and Far-Infrared Transitions of CH2CF2

Starting from the Watson A-reduced Hamiltonian and considering the infrared transitions with DeltaK(a) = 0, DeltaK(c) = +/-1 (A-type) or DeltaK(a) = +/-1, DeltaK(c) = +/-1 (B-type), and the far-infrared transitions with DeltaK(a) = 0, +/-2 and DeltaK(c) = +/-1, we calculate all the possible infrared absorption and far-infrared emission transitions of the v(4) and v(9) bands of 1,1-difluoroethylene (CH2CF2) pumped by 10P10 and 10P12 CO2 laser lines. We assign four previously unassigned CH2CF2 far-infrared laser lines (291.3 mum, 339.3 mum, 349.51 mum and 657.9 mum), where K-a and K-c represent the quantum number K of the limiting prolate top and the limiting oblate top, respectively. The 291.3 mum line is identified as being generated from the cascade transition. The assignment of the 288.5 mum line by Lafferty et al. (J. Mol. Spectrosc. 87(1981)416) is also confirmed.