title: Two-channel opto-acoustic diode laser spectrometer and fine structure of methane absorption spectra in 6070-6180 cm-1 region.
abstract: We describe the hardware and software of the high-sensitive two-channel opto-acoustic spectrometer with a near infrared diode laser. A semiconductor TEC-100 laser with outer resonator generates a continuous single-frequency radiation in the range of 6040-6300 cm-1 with spectral resolution better that 10 MHz. The newly designed model of photo-acoustic cells in the form of a ring type resonator was used in the spectrometer, and the system allows the measurement of a weak absorption coefficient equal to 1.4x10(-7) cm-1 Hz-1/2 with a laser radiation power of 0.003 W. The methane absorption spectra within a range of 6080-6180 cm-1 were measured with a spectral resolution of 10 MHz and the signal to noise ratio more than 10(3). Six hundred absorption lines were recorded, which is twice as many as in HITRAN-2004. The accurate measurements of the half-width and shift of methane unresolved triplet R3 of 2nu3 band permit us to determine values of the broadening and shift coefficients for CH4-air, CH4-N2, and CH4-SF6 mixtures.
authors.affiliation: Institute of Atmospheric Optics, SB RAS, 1 Akademicheskii Avenue, 634055 Tomsk, Russia. kvan@asd.iao.ru
authors.forename: V A
authors.initials: VA
authors.lastname: Kapitanov
authors.forename: Yu N
authors.initials: YN
authors.lastname: Ponomarev
authors.forename: I S
authors.initials: IS
authors.lastname: Tyryshkin
authors.forename: A P
authors.initials: AP
authors.lastname: Rostov
mesh_terms: D000162:Acoustics / Q000295:instrumentation*; D007834:Lasers; D008697:Methane / Q000032:analysis*; D011312:Pressure; D012984:Software; D013057:Spectrum Analysis / Q000295:instrumentation* / Q000379:methods*
chemical_list: D008697:Methane