Mary-Frances Jagod

Infrared spectroscopy of carbo‐ions. III. ν3 band of methyl cation CH+3

The infrared spectrum of the degenerate ν3 vibration–rotation band of methyl cation CH+3, one of the most fundamental carbo‐ions, has been observed and analyzed. The spectrum was observed in the frequency range of 3240–2960 cm−1 using the difference frequency laser system as the tunable coherent infrared source. A gas mixture of He:H2:CH4∼700:20:1 with a total pressure of ∼7 Torr was used for the ac discharge in an air‐cooled and a water‐cooled multiple inlet–outlet discharge tube. The velocity modulation method together with noise subtraction and the unidirectional multiple passing of the beam was used for high sensitivity. The spectral lines of CH+3 appeared amid many other lines of C2H+2 and C2H+3 but their widths and their response to chemical conditions gave a good initial clue for the identification. Over 200 absorption lines have been assigned to CH+3 and the isotopic species 13CH+3. The spectral pattern clearly shows that the equilibrium molecular structure is a planar, equilateral triangle as exp...

Infrared spectroscopy of carbo‐ions. V. Classical vs nonclassical structure of protonated acetylene C2H+3

The problem of classical vs nonclassical structure of protonated acetylene (vinyl cation) C2H+3 has been studied using high resolution infrared spectroscopy. The spectrum has been observed in the 3.2 μm region in air‐cooled and water‐cooled plasmas using C2H2:H2:He mixtures and in liquid nitrogen‐cooled plasmas using CH4:H2:He mixtures. The difference frequency spectrometer with the velocity modulation method has been used to conduct the Doppler‐limited, high sensitivity spectroscopy.The observed vibration–rotation pattern with the band origin at 3142.2 cm−1 has been identified as due to the antisymmetric CH stretching ν6 band of the C2H+3 ion with the nonclassical (bridged) structure. The observed spectral pattern was anomalous, but definitive assignments could be made for a part of the spectrum using the ground state combination differences which fit to the usual asymmetric rotor pattern. The discrimination between the classical and nonclassical structures is based on the observed spectral intensity pat...

Detection of H3(+) infrared emission lines in Saturn

Three emission lines of the ν 2 fundamental vibration-rotation band of H 3 + have been detected in the ionosphere of Saturn near and at its poles. The peak observed column density of H 3 + (at the south limb) is more than two orders of magnitude lower than the column density at the south pole of Jupiter and is less than that detected from Uranus. While the number and the signal-to-noise ratios of observed transitions are not sufficient to determine the temperature and abundance of H 3 + accurately, the observed emission intensities are consistent with a temperature of ≃800 K and total column density of ≃1.0×10 11 cm −2

Infrared spectroscopy of carbo-ions. VI: C-H stretching vibration of the acetylene ion C2H2+ and isotopic species

The infrared spectra of the band of the 2Π–2Π asymmetric hydrogen stretching vibration in the three isotopic acetylene ions C2H2+ (ν3), 13C2H2+ (ν3), and DCCH+ (ν1) have been observed and analyzed. The high resolution infrared spectra were recorded using a difference‐frequency laser spectrometer as the tunable coherent infrared source probing an ac glow discharge. Velocity modulation, noise subtraction, and unidirectional multipassing of the infrared beam through the discharge cell provided high sensitivity. C2H2+ was produced in a gas mixture of H2, He, and either CH4 or C2H2, with a total pressure of ≊7 Torr in multiple‐inlet–outlet air‐, water‐, and liquid‐nitrogen‐cooled discharge tubes; C2H2 freezing precluded its use in liquid‐N2‐cooled discharges. Complicated by a strong perturbation whose maximum occurred at N’=15 for F1 and N’=14 for F2, the assignment of the spectrum of normal C2H2+ was made possible by (1) fortuitous discharge conditions which provided unambiguous discrimination of C2H2+ lines ...

Infrared spectra of carboions. II. ν3 band of acetylene ion C2H+2(2Πu)

The infrared spectrum of the ν3 band of C2H+2(2Πu) has been observed and analyzed. This is the first observation of this fundamental molecular ion in any spectral range.

Infrared spectroscopy of carbo‐ions. IV. The A 2Πu–X 2Σ+g electronic transition of C−2

The infrared spectrum of the A 2Πu←X 2∑+g electronic transition of C−2 has been observed under high resolution and analyzed. Three bands (v’←v)=(0,0), (1,1) and (0,1) have been observed; the first two bands were observed by using the difference laser frequency system in the frequency range of 3960–3780 cm−1 and the last by using a diode laser in the frequency range of 2210–2120 cm−1. A gas mixture of 50 mTorr of acetylene and 7 Torr of He was used for the ac discharge in an air‐cooled and a water‐cooled multiple inlet–outlet discharge tube. The simplicity of the optimum gas mixture suggested that C−2 is produced directly by simple dissociative electron attachment of acetylene. Altogether 103 absorption lines have been observed and accurately measured. Most of them are P, Q, and R form branches of allowed F1↔F1, F2↔F2 transitions although some forbidden F1↔F2 transitions and O and S transitions have also been measured. The hot bands (1,1) and (0,1) have been observed with intensity which is less than that ...

Observation of the infrared spectrum of methyl cation CH+3

The vibration‐rotation infrared spectrum of the ν3 fundamental band of the methyl cation CH+3 has been observed using a difference frequency laser system. The analysis of the spectrum demonstrates the D3h symmetry of the ion. This work marks the beginning of high resolution spectroscopy of simple polyatomic hydrocarbon cations.

Inertial defects of planar symmetric top molecules

Abstract A general expression for the inertial defects of planar symmetric top molecules has been derived and applied to H 3 + , CH 3 + , C 3 H 3 + , and C 6 H 6 -type molecules. It has been found that the inertial derivatives a n αα for these molecules can be expressed in terms of Coriolis constants. This allowed us to find a sufficient number of relations among Coriolis constants that the number of independent Coriolis constants is equal to the number of independent force constants. A numerical calculation of the inertial defect has been conducted for benzene, using Wilsons GF matrix method, and compared with experimental values.

Spectral lines and distribution of H+3 in high rotational levels

Infrared spectrum of the ν2 fundamental band of H+3 in high rotational levels has been studied. Three motives for this study were (i) to provide laboratory data for the observation of astronomical objects in which a large abundance of H+3 exists at high temperature, (ii) to study kinetic energy distribution of H+3 in plasmas and to determine its rotational and translational temperatures, and (iii) to provide information on high rovibrational states for the variational calculations on the intramolecular dynamic of H+3. In order to increase the kinetic temperature, water‐cooled plasmas with helium dominated gas mixtures with He/H2∼5/0.6 torr were used. The observed rotational level in the ground state with the highest rotational quantum numbers was J=K=15 which has the rotational energy of 5091.6 cm−1. It was found from the observed relative intensities of the rovibrational transitions and linewidths that H+3 in the plasmas were in approximate thermal equilibrium with both rotational and translational tempe...

Laboratory infrared spectra of CH2D+ and HCCD+ and predicted microwave transitions

In order to provide radio-astronomical probes for CH 3 + and HCCH + , which play crucial roles in the chemical evolution of molecular clouds, infrared vibration-rotation spectra of their monodeuterated species have been measured. Rotational transitions of CH 2 D + and HCCD + are predicted