Ro-vibrational Stark-associated phenomena of small polyatomic molecules are modelled using extensive spectroscopic data generated as part of the ExoMol project. The external field Hamiltonian is built from the computed ro-vibrational line list of the molecule in question. The Hamiltonian we propose is general and suitable for any polar molecule in the presence of an electric field. By exploitin...

Continuous-wave mid-infrared radiation near 3.5 mm is generated by difference-frequency mixing of the output of a compact 1.1 1.5-mm dual-wavelength fiber amplif ier in periodically poled LiNbO3. The diode sidepumped amplif ier is constructed with double-cladding Yb-doped fiber followed by single-mode Er/Yb codoped fiber. Output powers of as much as 11 mW at 3.4 mm are obtained, and spectroscop...

We quantified eight parent volatiles (H2O, C2H6, HCN, CO, CH3OH, H2CO, C2H2, and CH4) in the Jupiter-family comet Tempel 1 using high-dispersion infrared spectroscopy in the wavelength range 2.8 to 5.0 micrometers. The abundance ratio for ethane was significantly higher after impact, whereas those for methanol and hydrogen cyanide were unchanged. The abundance ratios in the ejecta are similar t...

Ozonolysis is a major removal mechanism in the troposphere for unsaturated hydrocarbons which are emitted in large quantities from both natural and human sources. Now it is generally accepted that ozonolysis of alkenes proceeds via Criegee intermediates, highly reactive species postulated in 1949 by Rudolf Criegee. In the troposphere, Criegee intermediates are involved in several important atmo...

It is argued that the formation of the methoxy radical (CH3O) from H + H2CO may play an essential role in the reduction of CO to CH4. The rate coefficient for this reaction has been estimated using the approximate theory of J. Troe (1977a, J. Chem. Phys. 66, 4745) and transition state theory. We briefly discuss the implications of this reaction for the chemistry of CO on Jupiter, in the solar...

Centaurus A, the nearest AGN shows molecular absorption in the millimeter and radio regime. By observing the absorption with VLBI, we try to constrain the distribution of the gas, in particular whether it resides in the circumnuclear region. Analysis of VLBA observations in four OH and two H2CO transitions is presented here, as well as molecular excitation models parameterized with distance fro...

A revised set of temperature-dependent absorption cross sections for ultraviolet (UV) measurements of formaldehyde (H2CO) has been derived from two existing sets of laboratory cross sections, one using a Fourier transform spectrometer (FTS), and one using a grating instrument. This is conducted to satisfy the recommendation of the HITRAN Advisory Committee to provide a dataset with the spectral...

Conical intersections are degeneracies between multidimensional potential energy surfaces of molecular systems. It is well known that, besides these phenomena significantly modify the spectroscopic and dynamical properties molecules, their presence in a system has noticeable topological implications, as well. Such consequence appearance or geometric phase. not only occur nature but they can als...