Meeting the Challenge of High-Precision Spectroscopy: Laboratory-grade Atomic Models for Astrophysics

Grants and Contracts Details


In our unfolding era of high-precision astrophysics, which NASA missions such as JWST and Athena will carry forward, improvements in instrumentation will result in new information about the cosmos being recorded in unprecedented detail. Decoding such information from spectroscopic observations, our only means of uncovering the chemical and local thermodynamic conditions of light-emitting plasmas, requires atomic data of exquisite accuracy. Anything less than that should be viewed as systematic uncertainties introduced in the interpretation of these observations. We propose to create a high-fidelity atomic database to fully capture the potential for discovery latent in upcoming spectroscopic observations. Typically, two kinds of datasets exist for atomic models: Experimental datasets, which have level energies and transition Einstein A''''s of superb quality, but without any collision strength measurements. And theoretical datasets, which have good (but not superb) level energies and Einstein A''''s, and also possess collision strengths that are quite accurate, since they account for atomic resonances. The former can be used with the crude g-bar approximation to produce equally crude spectral predictions, while the latter can be used to produce rather accurate spectra but with typically incorrect transition wavelengths. This hampers line identification, and may be lead to incorrect conclusions about the dynamical state of nebulae. In our program, we will create a database of atomic models that capture the best elements of these types of datasets. We will draw experimental data from the NIST Atomic Spectra Database, and theoretical data from the OpenADAS database, to create hybrid datasets for the iso-electronic sequences from Li to Mg, for a total of 225 ions. For each ion, we will merge the experimental dataset with the theoretical to create a hybrid dataset. The effort begins by registering common energy levels in order to update the energies of the theoretical dataset to their experimental values. Transition probabilities are then updated to the new energy separations. Collision strengths, typically accurate to 15--20%, are used directly. The result is a complete hybrid model with energies and Einstein A''''s of superb accuracy and precision. The atomic synthesis code to be used with this program is already in place, so no new development is needed. We will make our results available in various formats, so they can be easily used by other codes, such as for extrasolar planetary atmospheres, stellar atmospheres, as well as plasma codes for the ISM / IGM. We will also include them in Cloudy''''s Stout database, and will benefit the broader community, which uses Cloudy in about 400 papers per year.
Effective start/end date2/1/231/31/26


  • National Aeronautics and Space Administration: $290,680.00


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