Charles F. Jackels

The two lowest energy 2A′ states of NO2

The 2A1 ground state of NO2 and the so‐called 2B2 excited state are shown to form a strongly coupled pair of 2A′ states when asymmetric distortion is considered. This coupling is of the Jahn–Teller type although the degeneracy between the states is accidental and the normal coordinates are not equivalent.

An ab initio potential‐energy surface study of several electronic states of NO2

The results of ab initio potential‐energy surface calculations are presented for 12 doublet and four quartet states of NO2. In several cases Cs as well as C2v conformations have been studied. The predicted equilibrium conformations and the character of the wavefunctions are discussed. Vertical excitation energies are given for 40 doublet and 12 quartet states. The electronic spectrum of NO2 is discussed, and barriers to photodissociation are estimated for several electronic states. Whether states will be strongly Jahn–Teller coupled by a symmetry‐reducing vibrational interaction depends on their potential surfaces and the character of their wavefunctions. This vibronic interaction in some cases is expected to produce non‐C2v equilibrium conformations.

A configuration interaction study of the ground state molecular properties of NO2

An ab initio SCF–CI wavefunction for the 2A1 ground state of NO2 has been calculated using a ’’double zeta plus polarization’’ quality basis set. The CI energy, −204.374346 a.u., is the lowest which has been reported for this molecule. The CI wavefunction is discussed and Mulliken population analyses are presented. Several one‐electron properties, including the magnetic hyperfine splitting parameters, are reported for both the SCF and CI wavefunction.

Experimental and ab initio investigation of the O–H overtone vibration in ethanol

The intracavity dye laser photoacoustic absorption spectra of ethanol, ethanol (1,1-d2), and ethanol (2,2,2-d3) are reported for the region 16 550–16 700 cm−1, which contains the O–H fourth overtone (ΔνOH=5) vibration. The distinct absorption bands have been assigned to the trans and gauche conformational isomers. Comparison of the spectra reveals a coupling between the OH and methylene CH vibrations in only the gauche conformer of ethanol, an effect that had not been observed in the fundamental spectrum. Ab initio electronic structure and vibrational frequency calculations are used to clarify and support the analysis of the ethanol OH vibrational spectrum and to evaluate the relative energies of the conformers.

The 1A1 π→π* state of formaldehyde

Abstract The 1 A 1 π→π * state of formaldehyde is predicted to be 11.2 eV above the ground state and not diffuse.

GCMS investigation of volatile compounds in green coffee affected by potato taste defect and the Antestia bug.

Potato taste defect (PTD) is a flavor defect in East African coffee associated with Antestiopsis orbitalis feeding and 3-isopropyl-2-methoxypyrazine (IPMP) in the coffee. To elucidate the manifestation of PTD, surface and interior volatile compounds of PTD and non-PTD green coffees were sampled by headspace solid phase microextraction and analyzed by gas chromatography mass spectrometry. Principal component analysis of the chromatographic data revealed a profile of surface volatiles distinguishing PTD from non-PTD coffees dominated by tridecane, dodecane, and tetradecane. While not detected in surface volatiles, IPMP was found in interior volatiles of PTD coffee. Desiccated antestia bugs were analyzed by GCMS, revealing that the three most prevalent volatiles were tridecane, dodecane, and tetradecane, as was found in the surface profile PTD coffee. Coffee having visible insect damage exhibited both a PTD surface volatile profile and IPMP in interior volatiles, supporting the hypothesis linking antestia bug feeding activity with PTD profile compounds on the surface and IPMP in the interior of the beans.