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Ryan Renganeschi
Introduction
Introduction
This study bridges laboratory spectroscopy and astrophysical modeling by providing molecular potential energy curves that improve predictions of molecular spectra in astronomical environments. Molecular potential curves derived from spectroscopic constants provide the fundamental input for astrophysical models which is used to identify molecular species and probe temperature, composition, and dynamics in stellar and interstellar environments. The interstellar medium contains everything from simple diatomic molecules to complex organic molecules, and their spectra are essential for understanding the chemistry and physics of the universe.
EXCITE Molecules Using Tunable Lasers
After constructing the experiment, molecules are excited to upper energy levels by lasers.
MEASURE Spectral Peaks From Experiment
Molecular emission lines are measured with high-resolution spectrometer in the lab.
EXTRACT spectroscopic constants
Spectral peaks are analyzed to obtain dissociation energy, depth of the well, etc. These constants encode the molecule’s structure.
CONSTRUCT potential energy curve (PEC) & COMPUTE rovibrational energy levels
Using step above, we generate PEC which determines molecular bond shape and rovibrational energy levels.
A PEC is derived from spectroscopic constants using Rydberg-Klein-Rees (RKR) computing method. For this we have developed Mathlab code. From PEC, we can compute vibrational and rotational energies which are important to calculate rovibrational energy levels and transition frequencies. This information is directly related to the wavelengths, intensities, and selection rules of the spectral lines we observe in space underpins molecular spectra used to identify species and diagnose physical conditions in interstellar environment. Astronomers observe the relative intensities of these spectral lines in a molecular cloud.
APPLY Boltzman analysis & INFER physical conditions of the interstellar medium
PEC-derived rovibrational energies are used to compare with observed line-intensity ratio. If populations of two states and their energies are known, using Boltzmann distribution method, one can extract the rotational and vibrational temperature of the interstellar medium.
From the step above, temperature, density, molecular abundance, chemical environment can be extracted.
Applications to Astrophysics
Nearly all molecular information in astrophysics comes from spectroscopy. Thus, accurate PECs are essential for interpreting molecular abundances, densities, temperatures, and chemical processes in interstellar clouds, star-forming regions, and planetary atmospheres. Without accurate PEC, one cannot reliably identify molecules or determine their physical conditions.
The images show Omega nebula (M17) – a dense, star forming region filled with molecular gases and dust. Spectral lines originating from rovibrational transitions (whose energies come from PECs) are used to determine temperature, density, & chemical composition of such region.
Acknowledgements
Acknowledgements
NSF (PHY-2309340), MU CAS and OARS are acknowledged.
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