Amino acids are the building blocks of proteins, and their detection in outer space thus has implications on the origin of life. They form a zwitterionic structure in aqueous environments while adopting a neutral configuration in the gas phase. We perform an experimental and computational study on the number of water molecules needed for zwitterion formation of β-alanine. Our density functional theory investigation reveals that a minimum of five water molecules are required to form and stabilize the zwitterion. A characteristic connecting water molecule located between the COO– and NH3 + groups is found to enhance the stability. This water molecule is also involved in a characteristic infrared active vibration at ≈1560 cm–1, which is slightly shifted with the number of surrounding water molecules and is located in a spectral region outside of water vibrations. A corresponding infrared signal is found in high-resolution experimental spectra of β-alanine and water in a solid para-hydrogen matrix.

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Triplet states are of great interest in current light-energy conversion strategies, as their creation through the singlet fission processes can overcome the Shockley-Queisser limit. We analyze the experimental possibilities for the detection of triplet states with ground state and linear response time dependent density functional calculations. We show that triplets can be clearly detected through their optical properties, that can be seen in photoabsorption and photeoelectron spectra, as well as in vibrational properties, that can be studied via infrared spectra.

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