Vibration-rotation bands of CO2 and OCS in the region 540–890 cm−1

The regions of the ν₂ band of CO₂ and the ν₁ band of OCS have been simultaneously measured by the Fourier transform spectrometer (1, 2). The resolution achieved was now about 0.0045 cm^?1. A total of eight “hot” bands of ¹²C¹⁶O₂ and ¹⁶O¹²C³²S and the fundamental bands ν₂ of ¹³C¹⁶O₂ and ν₁ of ¹⁶O¹²C³⁴S have been reported.     

High-resolution infrared spectrum of acetylene in the region of the bending fundamental v 5

The infrared spectrum of C₂H₂ in the region of the bending fundamental v ₅ has been studied at a resolution of about 0·015 cm^-1. The molecular constants G ₀(v ₅=1) = 730·3341 (1) cm^-1 and B ₀ = 1·176641 (2) cm^-1 have been derived. In addition to the fundamental, all the hot bands starting from the levels v ₄ and v ₅ have been investigated. The vibrational, vibration-rotation coupling and centrifugal constants for the excited vibrational states v ₅ = 2 and v ₄ = v ₅ = 1 have been derived using the vibration-rotation energy matrix.     

Photoacoustic Gas Analysis Using Interferometric Cantilever Microphone

Theoretical considerations and a simple but realistic model of the function of the cantilever‐based photoacoustic trace gas system are presented. The essential features of the cantilever dynamics, thermal characteristics, and noise models are derived. Some other related constructions are shown with the practical implementations of the real system.     

High resolution study of the group V impurities absorption in silicon

High resolution spectra of P-, As- and Sb-doped Si have allowed the determination of the “natural” width of the impurity lines for concentration in the range of 10¹⁴ at cm^?3 and below. The width of the P-lines makes possible the observation of the 5p₀ line, very close to the 4p_± line. In the Sb- and As-doped samples, an effect similar to concentration broadening is observed. Results on P- and Bi-doped samples at lower resolution give evidence of the observation of the 3d₀(P) line and of internal Stark effect in the Bi-doped sample.     

High resolution infrared spectrum of the ν4 band of DCCF

The bending vibration-rotation band ν₄ of DCCF was studied. The measurements were carried out with a Fourier spectrometer at a resolution of about 0.03 cm^?1. The constants B₀=0.29141(1)cm^?1, α₄=?5.02(2)×10^?4cm^?1, q₄=4.52(3)×10^?4cm^?1, and D₀=9.2(4)×10^?8cm^?1 were derived. The rotational analysis of the “hot” bands 2ν₄(Δ) ← ν₄(II) and 2ν₄(Σ⁺) ← ν₄(II) was performed. In addition, the “hot” bands ν₄ + ν₅ ← ν₅ were assigned. A set of vibrational constants involved was derived.     

High sensitivity in gas analysis with photoacoustic detection

Introduction of a new type of pressure sensor has been shown to improve orders of magnitude the sensitivity of a photoacoustic measurement system using a black body radiation source. A new pressure sensor was developed to overcome the limitations in the capacitive microphone technology and to obtain ultimate sensitivity in photoacoustic gas detection when using low modulation frequency below 500 Hz. The pressure sensor is a cantilever-type microphone with interferometric measurement of the sensor displacement. By using conventional filter-type photoacoustic setup with the cantilever microphone and a black body radiation source, we obtained a detection limit in the sub-ppb range for methane gas with 100 s measurement time.     

High and very high resolution spectroscopy of the vibrational-rotational states of non-rigid molecules with particular emphasis on ammonia

Using the vibration-inversion-rotation Hamiltonian for ammonia [V. ?pirko, J.M.R. Stone and D. Papou?ek, J. Mol. Spectrosc. 60 (1976) 159], a modified theory is worked out for the Δk = ± 3n interactions between the inversion-rotation energy levels in the ground and excited state of NH₃ which takes into account the large amplitude inversion motion.The high sensitivity submillimeter-wave spectrometer RAD has been used to measure the inversion and inversion-rotation transitions in the ν₂ state of ¹⁴NH₃ in the 18–37 cm^?1 region with microwave accuracy. The frequencies of the inversion-rotation transitions in the ground and ν₂ excited states have been measured with the 0.014 cm^?1 resolution in the 35–300 cm^?1 region with a Fourier transform spectrometer. The ν₂ band frequencies have been measured under Doppler limited resolution (<0.002 cm^?1) with a diode laser spectrometer and with 0.03 cm^?1 resolution using a grating spectrometer in the 10 μm region.By a least squares fit of these data and the data of the infrared-microwave two-photon and infrared heterodyne measurements of the ν₂ band, a set of the molecular constants for the ground and ν₂ state is obtained which reproduces the experimental data within the precision of the experiment.     

Ion-induced nucleation of dibutyl phthalate vapors on spherical and nonspherical singly and multiply charged polyethylene glycol ions

Dibutyl phthalate vapor nucleation induced by positive polyethylene glycol (PEG) ions with controlled sizes and charges was experimentally studied. The ions were produced by electrospray ionization, classified in a high-resolution differential mobility analyzer, and studied in a nano condensation nucleus counter of the mixing type. Ionic radii of PEG varied from 0.52 to 1.56 nm, including from singly to quadruply charged ions. Some of these ions are fully stretched chains, other are spherical, and others have intermediate forms, all of them having been previously characterized by mobility and mass spectrometry studies. Activation of PEG1080(+2) requires a supersaturation almost as high as that required for small singly charged ions and higher than for PEG1080(+). This anomaly is explained by the Coulombic stretching of the ion into a long chain, where the two charged centers appear to be relatively decoupled from each other. The critical supersaturation for singly charged spherical ions falls below Thomson's (capillary) theory and even below the already low values seen previously for tetraheptyl ammonium bromide clusters. Spherical PEG4120(+2) falls close to the Thomson curve. The trends observed for slightly nonspherical PEG4120(+3) and highly nonspherical (but not quite linear) PEG4120(+4) are intermediate between those of multiply charged spheres and small singly charged ions.