Investigating the Minimum Energy Principle in Searches for New Molecular Species - the Case of H2c3o Isomers

Recently, Lattelais et al. (2009) have interpreted aggregated observations of molecular isomers to suggest that there exists a “minimum energy principle”, such that molecular formation will favor more stable molecular isomers for thermodynamic reasons. To test the predictive power of this principle, we have fully characterized the spectra of the three isomers of C3H2O toward the well known molecular region Sgr B2(N). Evidence for the detection of the isomers cyclopropenone (c-C3H2O) and propynal (HCCCHO) is presented, along with evidence for the non-detection of the lowest zero-point energy isomer, propadienone (CH2CCO). We interpret these observations as evidence that chemical formation pathways, which may be under kinetic control, have a more pronounced effect on final isomer abundances than thermodynamic effects such as the minimum energy principle. Subject headings: astrochemistry, ISM molecules, ISM: abundances, ISM: clouds, molecular processes