Quantum-mechanical Rotational and Vibrational Signatures of Astrophyscially relevant Gas-Phase Stereo-isomeric Species of Leucine

The search for life-supporting molecules in outer space is an ever growing endeavour. Towards this, the quantum-mechanical computations supporting the astronomical spectroscopic observations are becoming valuable tools to unravel the complex chemical network in the interstellar medium (ISM). In the present work, quantum-mechanical computations are performed to obtain the rotational and vibrational line-data of gas-phase conformers of amino acid Leucine and its isomeric species predicted to be involved in its stereoinversion under the conditions of ISM. These species exhibit diverse chemistry including branched skeleton and zwitterionic ammonium ylides. Notably, the present work employs vibrational second order perturbation theory to account for anharmonic effects in rotational and vibrational transitions. The spectroscopic data computed in this work can assist in the detection of Leucine and its isomeric species in different regions of ISM.