- ID:
- ivo://CDS.VizieR/J/AcA/51/347
- Title:
- Partition functions of NiI-NiX
- Short Name:
- J/AcA/51/347
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The authors calculated atomic partition functions (APF) for nickel ions, Ni I - Ni X, using recent compilations of atomic energy levels. Observed sets of atomic energy levels were filled through levels predicted in quantum mechanics and autoionization levels. Therefore, our APFs include levels above those tabulated. APFs are functions of temperature T and the lowering of ionisation energy (LIE). LIE is the result of emitter-plasma interactions in gas that cause dissolution of the highest energy levels and is applied here in a cut-off approximation.
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- ID:
- ivo://CDS.VizieR/J/ApJ/796/36
- Title:
- PH_2_CN/CH_3_PH_2_ rotational transition frequency
- Short Name:
- J/ApJ/796/36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Millimeter/submillimeter spectra of PH_2_CN(~{X} ^1^A') and CH_3_PH_2_(~{X} ^1^A') have been recorded for the first time using direct absorption techniques. This work extends previous measurements of both molecules beyond the 10-50 GHz range. Both species were created in the presence of an AC discharge by the reaction of phosphorus vapor and either cyanogen and hydrogen (PH_2_CN) or methane (CH_3_PH_2_). Twelve rotational transitions of PH_2_CN were recorded over the region 305-422 GHz for asymmetry components K_a_=0 through 8. For CH_3_PH_2_, eight rotational transitions were measured from 210-470 GHz with K_a_=0 through 16; these spectra exhibited greater complexity due to the presence of internal rotation, which splits the K_a_=1, 2, and 3 asymmetry components into A and E states. Combined analyses of the millimeter/submillimeter and previous microwave data were performed for both molecules. For PH_2_CN, the spectra were fit with a Watson S-reduced asymmetric top Hamiltonian, resulting in more accurate rotational and centrifugal distortion constants. In the case of CH_3_PH_2_, an asymmetric top internal-rotation Hamiltonian was employed in the analysis, significantly improving the rotational and torsional parameters over previous microwave estimates. Searches for both molecules were subsequently conducted toward Sgr B2(N), using the 12 m telescope of the Arizona Radio Observatory (ARO). Neither species was identified, with abundance upper limits, relative to H_2_, of f(PH_2_CN/H_2_)<7.0x10^-12^ and f(CH_3_PH_2_/H_2_)<8.4x10^-12^. The nitrogen analogs NH_2_CN and CH_3_NH_2_ are therefore more abundant in Sgr B2(N) by factors of >2 and >200, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/575/A121
- Title:
- Photodesorption of H2O, HDO and D2O ice
- Short Name:
- J/A+A/575/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The HDO/H_2_O ratio measured in interstellar gas is often used to draw conclusions on the formation and evolution of water in starforming regions and, by comparison with cometary data, on the origin of water on Earth. In cold cores and in the outer regions of protoplanetary disks, an important source of gas-phase water comes from photodesorption of water ice. This research note presents fitting formulae for implementation in astrochemical models using previously computed photodesorption electronicciencies for all water ice isotopologues obtained with classical molecular dynamics simulations. The results are used to investigate to what extent the gas-phase HDO/H_2_O ratio reflects that present in the ice or whether fractionation can occur during the photodesorption process. Probabilities for the top four monolayers are presented for photodesorption of X (X=H,D) atoms, OX radicals, and X_2_O and HDO molecules following photodissociation of H_2_O, D_2_O, and HDO in H_2_O amorphous ice at ice temperatures from 10-100K. Significant isotope ects are found for all possible products: (1) H atom photodesorption probabilities from H_2_O ice are larger than those for D atom photodesorption from D_2_O ice by a factor of 1.1; the ratio of H and D photodesorbed upon HDO photodissociation is a factor of 2. This process will enrich the ice in deuterium atoms over time; (2) the OD/OH photodesorption ratio upon D_2_O and H_2_O photodissociation is on average a factor of 2, but the OD/OH photodesorption ratio upon HDO photodissociation is almost constant at unity for all ice temperatures; (3) D atoms are more ective in kicking out neighbouring water molecules than H atoms. However, the ratio of the photodesorbed HDO and H_2_O molecules is equal to the HDO/H_2_O ratio in the ice, therefore, there is no isotope fractionation when HDO and H_2_O photodesorb from the ice. Nevertheless, the enrichment of the ice in D atoms due to photodesorption can over time lead to an enhanced HDO/H_2_O ratio in the ice, and, when photodesorbed, also in the gas. The extent to which the ortho/para ratio of H_2_O can be modified by the photodesorption process is discussed briefly as well.
- ID:
- ivo://CDS.VizieR/J/ApJ/779/97
- Title:
- Photodissociation of CN
- Short Name:
- J/ApJ/779/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CN rovibrational photodissociation cross sections have been computed using ab initio derived potential curves and dipole transition moment functions adjusted to match asymptotic experimental constraints where available. Here, we report results for the electronic transitions ^2^{Sigma}^+^(4)<-X^2^{Sigma}^+^, ^2^{Sigma}^+^(5)<-X^2^{Sigma}^+^, ^2^{Pi}(4)<-X^2^{Sigma}^+^, and ^2^{Pi}(5)<-X^2^{Sigma}^+^. Partial cross sections for transitions from all 5581 rovibrational levels theoretically obtained for the ground electronic state X^2^{Sigma}^+^ were computed for a wavelength range that extends from 500{AA} to the dissociation threshold for each particular rovibrational state. Cross sections assuming a thermal Boltzmann distribution of rovibrational levels for gas temperatures between 500 to 5000 K are also obtained. Applications of the results to ultraviolet irradiated environments are discussed.
- ID:
- ivo://CDS.VizieR/J/A+AS/109/125
- Title:
- Photoionisation cross section
- Short Name:
- J/A+AS/109/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/A+A/529/A147
- Title:
- Photoionization cross sections of Selenium ions
- Short Name:
- J/A+A/529/A147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multi-configuration Breit-Pauli AUTOSTRUCTURE calculations of distorted-wave photoionization (PI) cross sections, and total and partial final-state resolved radiative recombination (RR) and dielectronic recombination (DR) rate coefficients for the first six ions of the trans-iron element Se. These calculations were motivated by the recent detection of Se emission lines in a large number of planetary nebulae. Se is a potentially useful tracer of neutron-capture nucleosynthesis, but accurate determinations of its abundance in photoionized nebulae have been hindered by the lack of atomic data governing its ionization balance. Our calculations were carried out in intermediate coupling with semi-relativistic radial wavefunctions. PI and recombination data were determined for levels within the ground configuration of each ion, and experimental PI cross-section measurements were used to benchmark our results. For DR, we allowed {Delta}n=0 core excitations, which are important at photoionized plasma temperatures.
- ID:
- ivo://CDS.VizieR/J/ApJ/667/1119
- Title:
- Photoionization of H in strong magnetic fields
- Short Name:
- J/ApJ/667/1119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A recently developed computational scheme, based on the complex-rotation method combined with a mixed Slater-Landau basis expansion, has been applied to calculations of photoionization from atomic hydrogen ground and excited states in a strong magnetic field typical of magnetic white dwarf stars. Photoionization cross sections are presented for the twelve states, 1s_0_, 2s_0_, 2p_0_, 2p_-1_, 3s'_0_, 3p_0_, 3p_-1_, 3d'_0_, 3d_-1_, 3d_-2_, 4f_-2_, and 4f_-3_, with magnetic field strengths from 23.5 to 2350MG.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A70
- Title:
- Plasma environment effects on Fe IX-XVI K lines
- Short Name:
- J/A+A/635/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the context of black-hole accretion disks, we have computed plasma environment effects on the atomic parameters used to model the decay of K-vacancy states in moderately charged iron ions, namely FeIX-FeXVI. We use the fully relativistic multiconfiguration Dirac-Fock (MCDF) method approximating the plasma electron-nucleus and electron-electron screenings with a time-averaged Debye-Huckel potential. Modified ionization potentials, K thresholds, wavelengths, radiative emission rates and Auger widths are reported for astrophysical plasmas characterized by electron temperatures and densities respectively in the ranges 10^5^-10^7^K and 10^18^-10^22^cm^-3^. This study confirms that the high-resolution X-ray spectrometers onboard the future XRISM and ATHENA space missions could detect the lowering of the K edges of these ions due to the extreme plasma conditions occurring in accretion disks around compact objects.
- ID:
- ivo://CDS.VizieR/J/ApJS/167/343
- Title:
- Plasma Recombination rate coefficients
- Short Name:
- J/ApJS/167/343
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Reliably interpreting spectra from electron-ionized cosmic plasmas requires accurate ionization balance calculations for the plasma in question. However, much of the atomic data needed for these calculations have not been generated using modern theoretical methods and are often highly suspect. This translates directly into the reliability of the collisional ionization equilibrium (CIE) calculations. We make use of state-of-the-art calculations of dielectronic recombination (DR) rate coefficients for the hydrogenic through Na-like ions of all elements from He up to and including Zn. Where measurements exist, these published theoretical DR data agree with recent laboratory work to within typically 35% or better at the temperatures relevant for CIE. We also make use of state-of-the-art radiative recombination (RR) rate coefficient calculations for the bare through Na-like ions of all elements from H through to Zn. Here we present improved CIE calculations for temperatures from 104 to 109 K using our data and the recommended electron impact ionization data of Mazzotta et al. (1998, Cat. <J/A+AS/133/403>) for elements up to and including Ni and Mazzotta (2000, private communication) for Cu and Zn. DR and RR data for ionization stages that have not been updated are also taken from these two additional sources.
- ID:
- ivo://CDS.VizieR/J/A+AS/114/363
- Title:
- Polarization profiles of H lines
- Short Name:
- J/A+AS/114/363
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we provide extensive tables of the coefficients that are needed in the calculation of the second-order moments of the polarization profiles of hydrogen lines. We cover all the transitions up to the level n=50, which is enough for many astrophysical applications. We also provide formulae which allow the calculation of the line and oscillator strengths and of the Einstein coefficients for the tabulated transitions.
