Using a semiclassical approach, we have calculated electron-, proton-, and ionized helium-impact line widths and shifts for 12 Be III and 27 B III multiplets. The obtained results have been compared with available experimental and theoretical data.
The Stark widths of singly ionized iron lines from a^6^D--z^6^D^o^ and a^6^D--z^6^F^o^ have been measured and compared with the predictions obtained on the basis of the Stark broadening regularities within similar spectra. The measurements were performed using a linear arc discharge plasma source within an electron density range of 5x10^22^m^-3^--2x10^23^m^-3^ and an electron temperature from 27000K to 30000K.
A statistical analysis of fine splitting of C IV, N V, O VI, Mg II, Al III and Si IV doublet absorption lines in quasar spectra is carried out in order to estimate a possible time variation of the fine-structure constant {alpha}= e^2^(h/2{pi})c (~1/137) over cosmological time scales t~10^10^yr. The observational basis of the analysis is a catalogue of 1414 pairs of wavelengths with redshifts z = 0.2 - 3.7, compiled from data published in 1980-1992. Robust statistical estimates like the ``trimmed mean'' are used as well as the least squares. No statistically significant time variation of {alpha} is found. The estimate {alpha}^-1^d{alpha}/dz = (-0.6+/-2.8)10^-4^ is obtained. For the 95% significance level, an upper bound on the rate of a relative variation of the fine-structure constant is |{alpha}^-1^d{alpha}/dz| < 5.6x10^-4^, which corresponds approximately to |{alpha}^-1^d{alpha}/dt| < 4x10^-14^ yr^-1^. This limit represents the strongest up-to-date restriction on the possible time variation of {alpha} for the epoch 0.2 <= z <~ 4.
Recent experimental works have studied the possible formation of hydroxyacetonitrile on astrophysical grains. It was formed from hydrogen cyanide (HCN) and formaldehyde (H_2_CO) in the presence of water under interstellar medium (ISM) conditions. Because these precursor molecules are abundant, hydroxyacetonitrile is an excellent target for interstellar detection. Previous studies of the rotational spectra were limited to 40GHz, resulting in an inaccurate line list when predicted up to the millimeter-wave range. We measured and analyzed its spectra up to 600GHz to enable is searches using cutting-edge millimeter and submillimeter observatories. The molecule 2-hydroxyacetonitrile exhibits large amplitude motion that is due to the torsion of the hydroxyl group. The analysis of the spectra was made using the RAS formalism available in the SPFIT program with Watson's S-reduction Hamiltonians. The submillimeter spectra of hydroxyacetonitrile, an astrophysically interesting molecule, were analyzed. More than 5000 lines were fitted with quantum number values reaching 75 and 25 for J and K_a_, respectively. An accurate line list and partition function were provided. A search for hydroxyacetonitrile in publicly available GBT PRIMOS project, IRAM 30m, and Herschel HEXOS observations of the Sgr B2(N) high-mass star-forming region resulted in a non-detection; upper limits to the column density were determined.
Astronomical surveys of interstellar molecules, such as those that will be available with the very sensitive ALMA telescope, require preliminary laboratory investigations of the microwave and submillimeter-wave spectra of new molecular species to identify these in the interstellar media. We build a linelist that should allow us to detect HCOOCD_2_H, provided it is present in the interstellar media in a suitable concentration.
Glycolaldehyde, a sugar-related interstellar prebiotic molecule, has recently been detected in two star-forming regions, Sgr B2(N) and G31.41+0.31. The detection of this new species increased the list of complex organic molecules detected in the interstellar medium (ISM) and adds another level to the chemical complexity present in space. Besides, this kind of organic molecule is important because it is directly linked to the origin of life. For many years, astronomers have been struggling to understand the origin of this high chemical complexity in the ISM. The study of deuteration may provide crucial hints.
The study of deuterated abundant molecules is recognized as important in understanding molecular complexity in star-forming regions. We seek to assign the laboratory millimeter and submillimeter wave rotational spectra of the CHD_2_CN and CH_2_DCN deuterated isotopologues of methyl cyanide over a wide frequency range in order to provide precise spectral predictions for observations.
