- ID:
- ivo://CDS.VizieR/J/A+A/619/A92
- Title:
- Laboratory analysis of methylketene
- Short Name:
- J/A+A/619/A92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The analysis of isomeric species of a compound observed in the interstellar medium is a useful tool to understand the chemistry of complex organic molecules. It could, likewise, assist to detect new species. Our goal consists on analyzing one of the two most stable species of the C_3_H_4_O family, methyl ketene, whose actual rotational parameters are not precise enough to allow its detection in the ISM. The obtained parameters will be used to search for it in the high-mass star-forming regions Orion KL and Sagittarius B2 as well as in the cold dark clouds TMC-1 in Taurus Molecular Cloud and Barnard 1 (B1-b).
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/825/150
- Title:
- Laboratory spectroscopy of sodium chloride (NaCl)
- Short Name:
- J/ApJ/825/150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report laboratory spectroscopy for the first time of the J=1-0 and J=2-1 lines of Na^35^Cl and Na^37^Cl in several vibrational states. The hyperfine structure has been resolved in both transitions for all vibrational levels, which permit us to predict with high accuracy the hyperfine splitting of the rotational transitions of the two isotopologues at higher frequencies. The new data have been merged with all previous works at microwave, millimeter, and infrared wavelengths and fitted to a series of mass-independent Dunham parameters and to a potential energy function. The obtained parameters have been used to compute a new dipole moment function, from which the dipole moment for infrared transitions up to {Delta}v=8 has been derived. Frequency and intensity predictions are provided for all rovibrational transitions up to J=150 and v=8, from which the ALMA data of evolved stars can be modeled and interpreted.
- ID:
- ivo://CDS.VizieR/J/PAZh/33/143
- Title:
- Laboratory studies of HNCO
- Short Name:
- J/PAZh/33/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Detailed studies of the internal motions of dark clouds using spectral lines of many molecules require a laboratory frequency accuracy of the order of a few m/s. Based on our laboratory studies of the HNCO rotational spectrum in the ground vibration state, we have increased significantly the accuracy of frequency calculations in a wide range of quantum numbers. We have achieved an 1{sigma} uncertainty for rotational transitions in the Ka=0,1 states recalculated to the Doppler velocity scale <2m/s for all frequencies <1.1THz. This value allows radio-astronomical measurements with an accuracy comparable to that of the highest-precision observations based on spectral lines of other molecules.
- ID:
- ivo://CDS.VizieR/J/ApJS/167/292
- Title:
- Laboratory transition probabilities for Gd II
- Short Name:
- J/ApJS/167/292
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radiative lifetimes, accurate to +/-5%, have been measured for 49 even-parity and 14 odd-parity levels of GdII using laser-induced fluorescence. The lifetimes are combined with branching fractions measured using Fourier transform spectrometry to determine transition probabilities for 611 lines of Gd II. This work is the largest-scale laboratory study to date of GdII transition probabilities and the first using a high-performance Fourier transform spectrometer. This improved data set has been used to determine a new solar photospheric Gd abundance, log{epsilon}=1.11+/-0.03. Revised Gd abundances have also been derived for the r-process-rich metal-poor giant stars CS 22892-052, BD +17 3248, and HD 115444. The resulting Gd/Eu abundance ratios are in very good agreement with the solar system r-process ratio. We have employed the increasingly accurate stellar abundance determinations, resulting in large part from the more precise laboratory atomic data, to predict directly the solar system r-process elemental abundances for Gd, Sm, Ho, and Nd. Our analysis of the stellar data suggests slightly higher recommended values for the r-process contribution and total solar system values, consistent with the photospheric determinations, for the elements for Gd, Sm, and Ho.
- ID:
- ivo://CDS.VizieR/J/ApJ/849/5
- Title:
- L-edge single and multiple photoionization of Fe+
- Short Name:
- J/ApJ/849/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Absolute cross-sections for m-fold photoionization (m=1, ..., 6) of Fe+ by a single photon were measured employing the photon-ion merged-beams setup PIPE at the PETRA III synchrotron light source, operated by DESY in Hamburg, Germany. Photon energies were in the range 680-920eV, which covers the photoionization resonances associated with 2p and 2s excitation to higher atomic shells as well as the thresholds for 2p and 2s ionization. The corresponding resonance positions were measured with an uncertainty of +/-0.2eV. The cross-section for Fe+ photoabsorption is derived as the sum of the individually measured cross-sections for m-fold ionization. Calculations of the Fe+ absorption cross-sections were carried out using two different theoretical approaches, Hartree-Fock including relativistic extensions and fully relativistic multiconfiguration Dirac-Fock. Apart from overall energy shifts of up to about 3eV, the theoretical cross-sections are in good agreement with each other and with the experimental results. In addition, the complex de-excitation cascades after the creation of inner-shell holes in the Fe+ ion were tracked on the atomic fine-structure level. The corresponding theoretical results for the product charge-state distributions are in much better agreement with the experimental data than previously published configuration-average results. The present experimental and theoretical results are valuable for opacity calculations and are expected to pave the way to a more accurate determination of the iron abundance in the interstellar medium.
- ID:
- ivo://CDS.VizieR/J/A+A/432/369
- Title:
- Leiden Atomic and Molecular Database (LAMDA)
- Short Name:
- J/A+A/432/369
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Atomic and molecular data for the transitions of a number of astrophysically interesting species are summarized, including energy levels, statistical weights, Einstein A-coefficients and collisional rate coefficients. Available collisional data from quantum chemical calculations and experiments are extrapolated to higher energies (up to E/k~1000K). These data, which are made publically available through the WWW at http://www.strw.leidenuniv.nl/~moldata , are essential input for non-LTE line radiative transfer programs. An online version of a computer program for performing statistical equilibrium calculations is also made available as part of the database. Comparisons of calculated emission lines using different sets of collisional rate coefficients are presented. This database should form an important tool in analyzing observations from current and future (sub)millimetre and infrared telescopes.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A51
- Title:
- Levels and rate coefficients of the Fe-L
- Short Name:
- J/A+A/627/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A major challenge in X-ray spectral modeling is the Fe-L spectrum, which is basically a complex assembly of n>=3 to n=2 transitions of Fe ions in different ionization states, affected by a range of atomic processes such as collisional excitation, resonant excitation, radiative recombination, dielectronic recombination, and innershell ionization. In this paper we perform a large-scale theoretical calculation on each of the processes with the flexible atomic code (FAC), focusing on ions of FeXVII to FeXXIV that form the main body of the Fe-L complex. The calculation includes a large set of energy levels with a broad range of quantum number n and l, taking into account the full-order configuration interaction and all possible resonant channels between two neighboring ions. The new data are found to agree within 20% with the recent individual R-matrix calculations for the main FeL lines, although the discrepancies become significantly larger for the weaker transitions, in particular for FeXVIII, FeXIX, and FeXX. By further testing the new FAC calculations with the high-quality RGS data from 15 elliptical galaxies and galaxy clusters, we note that the new model gives systematically better fits than the current SPEX v3.04 code, and the mean Fe abundance decreases by 12%, while the O/Fe ratio increases by 16% compared with the results from the current code. Comparing the FAC fit results to those with the $R$-matrix calculations, we find a temperature-dependent discrepancy of up to 10% on the Fe abundance between the two theoretical models. Further dedicated tests with both observed spectra and targeted laboratory measurements are needed to resolve the discrepancies, and ultimately to get the atomic data ready for the next high-resolution X-ray spectroscopy mission.
- ID:
- ivo://CDS.VizieR/J/ApJ/748/L25
- Title:
- Li-Be-B measurements using SIMS
- Short Name:
- J/ApJ/748/L25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Beryllium-10 is a short-lived radionuclide (t_1/2_=1.4Myr) uniquely synthesized by spallation reactions and inferred to have been present when the solar system's oldest solids (calcium-aluminum-rich inclusions, CAIs) formed. Yet, the astrophysical site of ^10^Be nucleosynthesis is uncertain. We report Li-Be-B isotope measurements of CAIs from CV chondrites, including CAIs that formed with the canonical ^26^Al/^27^Al ratio of ~5x10^-5^ (canonical CAIs) and CAIs with Fractionation and Unidentified Nuclear isotope effects (FUN-CAIs) characterized by ^26^Al/^27^Al ratios much lower than the canonical value. Our measurements demonstrate the presence of four distinct fossil ^10^Be/^9^Be isochrons, lower in the FUN-CAIs than in the canonical CAIs, and variable within these classes. Given that FUN-CAI precursors escaped evaporation-recondensation prior to evaporative melting, we suggest that the ^10^Be/^9^Be ratio recorded by FUN-CAIs represents a baseline level present in presolar material inherited from the protosolar molecular cloud, generated via enhanced trapping of galactic cosmic rays. The higher and possibly variable apparent ^10^Be/^9^Be ratios of canonical CAIs reflect additional spallogenesis, either in the gaseous CAI-forming reservoir, or in the inclusions themselves: this indicates at least two nucleosynthetic sources of ^10^Be in the early solar system. The most promising locale for ^10^Be synthesis is close to the proto-Sun during its early mass-accreting stages, as these are thought to coincide with periods of intense particle irradiation occurring on timescales significantly shorter than the formation interval of canonical CAIs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/3323
- Title:
- (Li-He)^+^ collisions non-radiative processes
- Short Name:
- J/MNRAS/449/3323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A full quantum study of non-radiative inelastic processes in lithium-helium ion-atom collisions is presented. The study uses the 13 lowest-lying electronic molecular states of LiHe^+^ of the ^1^{Sigma}^+^, ^3^{Sigma}^+^, ^1^{Pi}, and ^3^{Pi} symmetries. Radial non-adiabatic coupling matrix elements between states of the same symmetry are calculated. Quantum non-adiabatic nuclear dynamics is studied by the reprojection method, which takes into account all non-adiabatic couplings, including those that exhibit non-vanishing asymptotic values. The energy dependence of the cross-sections and temperature dependence of the rate coefficients for all partial processes between the scattering channels is determined. It is shown that the temperature dependence of rate coefficients for the non-radiative and the radiative processes behave differently: the non-radiative rate coefficients increase with increasing temperature, while the radiative rate coefficients decrease. Consequently, in the depopulation of the same scattering channel the non-radiative processes dominate in high-temperature environments, whereas at low temperature, such as in interstellar molecular clouds, the radiative processes are typically more efficient.
- ID:
- ivo://CDS.VizieR/J/A+A/528/A69
- Title:
- Li-like iso-electronic sequence
- Short Name:
- J/A+A/528/A69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our calculated data including energy levels, radiative decay rates and effective collision strengths for all the transitions among the 24 fine-structure valence levels (14 LS levels) and 180 core-excited levels (80 LS levels) of Li-like iso-electronic sequence, i.e. those with configurations: 1s2 {2, 3,4,5}l, 1s 2l {2, 3, 4}l', (l=s, p, d, f and g). The effective collision strengths at 13 temperatures ranging from 2x10^2^(q+1)^2^ to 2x10^6^(q+1)^2^K, where q is the residual charge of ions, i.e. Z-3, have been calculated using the ICFT R-matrix method. The data format adopts ADAS adf04 format, see the file at website http://www.adas.ac.uk/man/appxa-04.pdf Filename format: charge.dat For example O^5+^, o5.dat
