High-sensitive Fourier-transform spectroscopy with short-base multipass absorption cells

LED-based Fourier transform spectroscopy of H218O in the 15,000–16,000 cm−1 range

“…The spectra [16] were calculated by S.A. Tashkun (IAO SB RAS, Tomsk, Russia) using Schwenke's program VTET [25] and based on the results of Schwenke and Partridge (SP) [26,27]. As the result of the conducted analysis, we were able to determine 426 rotational levels for eleven vibrational states of H 2 18 O and 72 rotational levels for six vibrational sates of H 2 17 O (see Table 2). It should be noted that the deviations of the (v SP ) for two bands, ν 1 þν 2 þ3ν 3 and 4ν 1 þ ν 2 , are shown in dv is not critically large because of its smooth change as the rotational numbers J and K a grow, thus enabling one to reliably assign the lines in the given spectral region.…”

“…Detailed information on the absorption of H 2 18 O in the spectral range 15,000-16,000 cm . The data from Ref.…”

“…4 were obtained from the SP variational calculation [16]. The energy levels obtained in this study were used to generate a line list of more than 1300H 2 18 O line positions between 15,000 and 16,000 cm …”

“…[1]) nor the databases [14,15] contain the information on the absorption by H 2 18 O or H 2 17 O between 14,500 and 16,500 cm À 1 . On the other hand, according to variational calculations [16], there are at least three bands in this region: 2ν 1 þ3ν 2 þν 3 (ν 0 ¼15,050 cm À 1 ), 2ν 1 þν 2 þ2ν 3 (ν 0 ¼15,265 cm À 1 ) and 3ν 1 þν 2 þ ν 3 (ν 0 ¼ 15,280 cm À 1 ) with respective integral intensities 1.4 Â 10 À 23 , 0.44 Â 10 À 23 , and 8.8Â 10 À 23 cm/molecule at 296 K. It was shown [17,18] that the use of high luminance LED emitters as the light sources in Fourier transform spectrometers permits one to enhance their threshold sensitivity in the visible range by orders of magnitude. The purpose of this research is to investigate thoroughly the Н 2 18 О absorption spectrum between 15,000 and 16,000 cm À 1 recorded by a Fourier transform spectrometer using the high luminance LEDs as light sources.…”

“…Applying 25-cm multipath cells with a total absorbing path of 10 m, we were able to measure the centers and intensities of about 700 lines of the H 2 18 O molecule associated with eleven rotational-vibrational bands of the 4ν and 4ν þδ resonance polyads. Preliminary results of the spectrum identification for the 15,000-15,700 cm À 1 region were reported in Ref.…”