6 research outputs found
Terahertz Wave Generation from Liquid Gas
International audienc
Broadband Terahertz Wave Generation from "Liquid-like" media
We present results of the research on generation of THz radiation in «liquid like» media under irradiating them with high-intensity femtosecond optical pulses: gas clusters and liquid nitrogen. We used a «dual-frequency» scheme when emissions of the main laser frequency and its second harmonic are mixed in the same medium
Generation of Terahertz Radiation from Liquid Nitrogen
International audienc
Terahertz wave generation from liquid nitrogen
International audienc
Nitroxoline Molecule: Planar or Not? A Story of Battle between π–π Conjugation and Interatomic Repulsion
The
conformational properties of the nitro group in nitroxoline (8-hydroxy-5-nitroquinoline,
NXN) were investigated in the gas phase by means of gas electron diffraction
(GED) and quantum chemical calculations, and also with solid-state
analysis performed using terahertz time-domain spectroscopy (THz-TDS).
The results of the GED refinement show that in the equilibrium structure
the NO<sub>2</sub> group is twisted by angle ϕ = 8 ± 3°
with respect to the 8-hydroxyoquinoline plane. This is the result
of interatomic repulsion of oxygen in the NO<sub>2</sub> group from
the closest hydrogen, which overcomes the energy gain from the π–π
conjugation of the nitro group and aromatic system of 8-hydroxyoquinoline.
The computation of equilibrium geometry using MP2/cc-pVXZ (X = T,
Q) shows a large overestimation of the ϕ value, while DFT with
the cc-pVTZ basis set performs reasonably well. On the other hand,
DFT computations with double-ζ basis sets yield a planar structure
of NXN. The refined potential energy surface of the torsion vibration
the of nitro group in the condensed phase derived from the THz-TDS
data indicates the NXN molecule to be planar. This result stays in
good agreement with the previous X-ray structure determination. The
strength of the π-system conjugation for the NO<sub>2</sub> group
and 8-hydroxyoquinoline is discussed using NBO analysis, being further
supported by comparison of the refined semiexperimental gas-phase
structure of NXN from GED with other nitrocompounds