China
Victor Lee
CHEM 113
4/5/2013
The Spectroscopy of Interstellar Anions Dr. Ryan Fortenberry presented about one of the greatest mysteries in spectroscopy, which involved these diffuse interstellar bands spectra of space. No one has been able to conclusively determine these specific bands, but after thought, Fortenberry speculated that these could potentially be absorption bands of anions due to various other observations from previous reports about these findings. Fortenberry ran calculations using the coupled-cluster theory to get the most accurate results, and it has been determined that several small anions, such as CH2CN-, had similar excitation energies compared to that experimental benchmark. However, several other ground state excitation energies, and that there was a correlation with silicon because there were some fairly accurate CCSD calculations that came out of molecules that contained silicon in there. Using these calculations, one can then use the spectra that generated with these calculations, and compare it with the interstellar bands to determine if there really are anions in space. After that seminar, I wondered that even if there potentially anions in space, since anions are not really stable, would the anions much rather form ionic bonds with hydrogen to neutralize their charge? Anions in general are fairly unstable, and that since they would prefer to be ionized immediately, then one would see bonding in the spectra. Professor Kelley asked an interesting question which was since 99% of these bands were already discovered, was there any reason to figure out the other 1% of those bands. I thought that if we can figure out 99% of what is in the spectrum, then I also wondered how computationally expensive would it be to determine all of the peaks that occur in the spectrum since that 1% could actually be only dust. No one can be sure what these bands are, but there are studies that are going on that would help guide our knowledge to
CHEM 113
4/5/2013
The Spectroscopy of Interstellar Anions Dr. Ryan Fortenberry presented about one of the greatest mysteries in spectroscopy, which involved these diffuse interstellar bands spectra of space. No one has been able to conclusively determine these specific bands, but after thought, Fortenberry speculated that these could potentially be absorption bands of anions due to various other observations from previous reports about these findings. Fortenberry ran calculations using the coupled-cluster theory to get the most accurate results, and it has been determined that several small anions, such as CH2CN-, had similar excitation energies compared to that experimental benchmark. However, several other ground state excitation energies, and that there was a correlation with silicon because there were some fairly accurate CCSD calculations that came out of molecules that contained silicon in there. Using these calculations, one can then use the spectra that generated with these calculations, and compare it with the interstellar bands to determine if there really are anions in space. After that seminar, I wondered that even if there potentially anions in space, since anions are not really stable, would the anions much rather form ionic bonds with hydrogen to neutralize their charge? Anions in general are fairly unstable, and that since they would prefer to be ionized immediately, then one would see bonding in the spectra. Professor Kelley asked an interesting question which was since 99% of these bands were already discovered, was there any reason to figure out the other 1% of those bands. I thought that if we can figure out 99% of what is in the spectrum, then I also wondered how computationally expensive would it be to determine all of the peaks that occur in the spectrum since that 1% could actually be only dust. No one can be sure what these bands are, but there are studies that are going on that would help guide our knowledge to