Lowest Overtone and Combination Levels of DCCI: The Fermi Resonance v3 = 1/v5 = 2.
The infrared spectrum of deuterated monoiodoacetylene DCCI in the region of 220-550 cm-1 has been studied at a resolution of 0.0020 cm-1. The hot bands nu3 <-- nu15 and 2nu0,25 <-- nu15 have been analyzed by considering especially the Fermi resonance v3 = 1/v5 = 2. In the next layer of the hot bands (nu3 + nu5)1 <-- nu3, (nu3 + nu5)1 <-- 2nu0,25 and 3nu1,35 <-- 2nu25 the same Fermi resonance appears between v3 = v5 = 1 and v5 = 3. In addition, various l resonances at the overtone levels have been considered. As a result, the vibrational and rotational constants for the level systems v3 = 1/v5 = 2 and v3 = v5 = 1/v5 = 3 together with the resonance parameters have been obtained. Copyright 1999 Academic Press.
Simultaneous Analysis of the Rovibrational Levels υ4=1, 2, and 3 of HCCI and DCCI Based on Infrared Spectra
Abstract The energy levels υ 4 =1, υ 4 =2, and υ 4 =3 of DCCI have been analyzed by using the fundamental ν 4 1 (470–520 cm −1 ) and the overtone 2ν 4 0 (955–1005 cm −1 ) bands together with the hot bands 2ν 4 0,2 ←ν 4 1 , 3ν 4 1,3 ←2ν 4 0,2 , and 3ν 4 1 ←ν 4 1 . In the case of HCCI the previously studied hot bands connected to ν 4 have been completed by adding 3ν 4 1 ←ν 4 1 into the analysis. The various l -type resonances have been taken into account in the analyses of both the isotopomers. Furthermore, the Coriolis resonance between the close-lying ν 3 and ν 4 of DCCI has been considered. Altogether, accurate values for the molecular constants and the resonance parameters have been obtained from simultaneous analysis and they have been compared with those from separate analyses for different levels.
Turbulent boundary layer wall‐pressure fluctuations downstream from an abrupt change in surface roughness
Spectra of wall‐pressure fluctuations beneath a turbulent boundary layer have been investigated immediately downstream from an abrupt change in surface roughness, from slightly rough to very rough. Over the measurable frequency band (400 Hz to 7 kHz), the spectra in the first 150 mm scale on wall variables. This indicates that the motions responsible for the pressure fluctuations measured in this region are very close to the wall. Farther downstream this scaling procedure breaks down. It is suggested that the initially thin internal layer behaves independently of the flow external to it until it has grown appreciably and only then interacts with the outer boundary layer. It was found that, for all frequencies measured, the dimensional spectral level decreases initially then rises to a maximum at 250 mm from the roughness change before decreasing once more. The position of the maximum is close to where the internal layer ceases to have a distinct edge.