Gao Xiao-ming

Highly Sensitive Tunable Diode Laser Absorption Spectroscopy of CO2 Around 1.31 μm

Fifteen new absorption lines were observed when studying CO_2 absorption spectroscopy by wavelength modulation(WM) technique with a DFB laser.The line intensity we can detect is 2.251 63×10~(-27) cm~(-1)·(moleculecm~(-2))~(-1) at 6.67×10~2 Pa pressure,corresponding to an absorbance of 3.88×10~(-8).The overtone spectra of CO_2 around 1.31 μm have been measured with a tunable diode laser and the corresponding spectral parameters(positions,intensities,and self-broadening coefficients) are presented.

Absorption measurements for highly sensitive diode laser of CO2 near 1.3μm at room temperature

Fifteen new absorption lines were observed when studying CO2 absorption spectroscopy by wavelength modulation technique with a distributed feedback laser. The overtone spectra of CO2 around 1.31μm and the corresponding spectral parameters (i.e. positions, intensities, self-broadening coefficients) are presented. The intensity of the weakest line detected is 2.25163×10−27cm−1/(molecule.cm−2) at the pressure of 667Pa, with a corresponding absorption of 3.88×10−8.

Multi-wavelength measurements of aerosol optical absorption coefficients using a photoacoustic spectrometer

The atmospheric aerosol absorption capacity is a critical parameter determining its direct and indirect effects on climate. Accurate measurement is highly desired for the study of the radiative budget of the Earth. A multi-wavelength (405 nm, 532 nm, 780 nm) aerosol absorption meter based on photoacoustic spectroscopy (PAS) invovling a single cylindrical acoustic resonator is developed for measuring the aerosol optical absorption coefficients (OACs). A sensitivity of 1.3 Mm−1 (at 532 nm) is demonstrated. The aerosol absorption meter is successfully tested through measuring the OACs of atmospheric nigrosin and ambient aerosols in the suburbs of Hefei city. The absorption cross section and absorption Angstrom exponent (AAE) for ambient aerosol are determined for characterizing the component of the ambient aerosol.

Low temperature laser absorption spectra of methane in the near-infrared at 1.65 μm for lower state energy determination

Direct absorption spectra of the 2ν3 band of methane (CH4) from 6038 to 6050 cm−1 were studied at different low temperatures using a newly developed cryogenic cell in combination with a distributed feedback (DFB) diode laser. The cryogenic cell can operate at any stabilized temperature ranging from room temperature down to 100 K with temperature fluctuation less than ±1 K within 1 hour. In the present work, the CH4 spectra in the range of 6038–6050 cm−1 were recorded at 296, 266, 248, 223, 198, and 176 K. The lower state energy E″ and the rotational assignment of the angular momentum J were determined by a “2-low-temperature spectra method using the spectra recorded at 198 and 176 K. The results were compared with the data from the GOSAT and the recently reported results from Campargue and co-workers using two spectra measured at room temperature and 81 K. We demonstrated that the use of a 2-low-temperature spectra method permits one to complete the E″ and J values missed in the previous studies.

Chaotic Motion in a Harmonically Excited Soliton System

The influence of a soliton system under an external harmonic excitation is considered. We take the compound KdV-Burgers equation as an example, and investigate numerically the chaotic behavior of the system with a periodic forcing. Different routes to chaos such as period doubling, quasi-periodic routes, and the shapes of strange attractors are observed by using bifurcation diagrams, the largest Lyapunov exponents, phase projections and Poincare maps.

High Resolution and High Sensitivity Measurement of Methane at 1.51 μm

The high-resolution absorption spectrum of CH4 at 1.51 μm is observed by direct absorption spectroscopy technique with a White absorption cell. Multi-peak fitting technique is adopted to reveal line positions and line intensities of CH4 from 6608 cm−1 to 6625 cm−1. Special attention is paid on the determination of the line positions, and the accuracy is better than ±0.002 cm−1. A minimum measurable absorption of 2.1×10−8 (3σ) has been achieved based on the measured direct absorption spectroscopy.