Spectroscopy of laser-ablated buffer-gas-cooled PbO at 4 K and the prospects for measuring the electric dipole moment of the electron

We demonstrate production of cold lead monoxide (PbO) molecules by laser ablation in a cryogenic cell filled with helium buffer gas and cooled by a cryostat to a temperature of 4 K. The molecules are probed by laser-induced fluorescence excited in the X→B band. The molecules thermalize with the buffer gas, both translationally and rotationally, in less than 30 ms after the ablation pulse. A single ablation pulse fired at the solid PbO sample yields about 10¹² cold molecules. We present an analysis indicating that buffer-gas cooled PbO molecules excited to either the a or B state could be effectively used to search for the permanent electric dipole moment of the electron.