Evard Immanuel Hjelt (1855–1921): Finnish Chemist and Historian of Chemistry

Although today unjustly neglected abroad and often even in his native land, Edvard Immanuel Hjelt (1855–1921), was an exceptionally gifted, dedicated, and multifaceted individual who made important contributions to chemistry, the history of chemistry, politics, and the management of national and international affairs. Little information about him is available in English. The present article supplements the only two English sources available [1, pp 66–83; 2] and makes this chemist-statesman better known to those chemists and historians who do not read Swedish or Finnish.In this section we present articles by leading scientific historians that chronicle the important events, persons, and publications that make up the rich history of chemical science. The history, and the articles in this ection often make that very clear. Chemists and their research are always influenced by current events. These articles are intended to describe the setting in which important discoveries occurred and to humazine their discoveres.     

Refined local mode analysis of the stretching vibrational levels of C2D2

Dideuteroacetylene, C₂D₂, is a remarkable species for which the stretch-bend separability of the vibrational states is such that all the experimentally known stretching levels can be reproduced with an rms of 1.1 cm^?1 by using a simple stretching coordinate Hamiltonian model. The only two levels which deviate significantly from the calculations point out the effect of the 1/244 stretch-bend resonance previously identified. The local mode parameters retrieved from the fit of the experimental levels allow for a very satisfactory prediction of the available energy levels of the ¹²C¹³CD₂ species. A comparison between the local mode and normal mode approaches is presented.     

High-resolution infrared and laser photoacoustic spectroscopy of monochloroacetylene

High-resolution vibration—rotation spectra of monochloroacetylene (HCCCl) have been recorded in two different wavenumber regions. Fourier transform infrared interferometer measurements in the 4000–10000cm^?1 range have been performed with a resolution of 0.005–0.016cm^?1 and titanium: sapphire ring laser intracavity photoacoustic measurements in the 12500–12600cm^?1 and 12800–12860cm^?1 regions have been carried out with a Doppler-limited resolution of about 0.02 cm^?1. Altogether, 40 vibrational bands belonging to the HCC³⁵ Cl and 15 bands belonging to the HCC³⁷ Cl isotopic species have been rotationally assigned. A vibrational model, based on the conventional rectilinear normal coordinate theory including anharmonic Fermi, Darling—Dennison and vibrational l-type doubling resonances, has been used to attach vibrational labels to the bands. This approach is found to describe well the rovibrational energy level structure at least in the energy range covered in this work. The model shows that the CH oscillator becomes decoupled from the rest of the molecule as vibrational energy increases.     

Calculation of spectroscopic parameters and vibrational overtones of methanol

A high-level quartic ab initio potential energy surface of methanol has been used to calculate spectroscopic constants of the ¹²CH₃OH molecule. These include coefficients of quartic anharmonic resonance terms, Darling-Dennison constants, for stretching states. A model expressed in terms of dimensionless normal coordinates has been employed in the calculation of O—H and C—H stretching vibrational states in high-overtone regions. Both cubic Fermi and quartic Darling-Dennison anharmonic coupling terms have been included in the model in order to take into account strong resonances between different states. The nonlinear least-squares method has been used to optimize some of the model parameters employing experimental term values of ¹²CH₃OH as data. Vibrational assignments are suggested for the first C—H stretching overtone region.     

Chemistry and Politics: Edvard Immanuel Hjelt (1855–1921)

Chemists who have made important contributions to politics, although a rare breed, date from the very inception of our science. Antoine-Laurent Lavoisier (1743–1794), the founder of modern chemistry, spent most of his time working as a financier, economist, accountant, banker, treasurer, academician, statistician,     

Anharmonic force field for methanol

An ab initio quartic anharmonic force field for methanol has been calculated at the equilibrium position using the CCSD(T) method for the structure and the harmonic potential energy surface, and the MP4(SDQ) method for the anharmonic part of the surface. A triple zeta basis set was employed with symmetrized curvilinear internal valence coordinates in all calculations. The internal coordinate force field constants have been transformed into force constants in the dimensionless normal coordinate representation for various isotopomers. Vibrational term values for CH₃OH, CH₃OD, CD₃OH, and CD₃OD have been obtained using second order perturbation theory. Particular care has been devoted to the inclusion of Fermi resonance interactions between different vibrational states. A good accuracy has been achieved in the calculation of the fundamentals for all the isotopomers, the mean absolute error being 5.8 cm^?1.     

Computational resolution enhancement: congested overtone spectrum of diacetylene

The first CH stretching overtone band system of diacetylene (1,3-butadiyne) in the range of 6350–6750 cm^?1 has been recorded with a high resolution Fourier transform infrared interferometer at room temperature. Although the spectrum obtained may be resolved rotationally, two different computational procedures have been used to enhance the resolution due to severe congestion in the central parts of the band system. It has become possible both to find one new band and to achieve higher precision. Altogether five bands with the lower state being the ground vibrational state have been analysed rotationally. The results obtained are discussed in the context of a previous molecular beam study of a small part of the same band system.