In heating and cooling apparatus, molecules of working gas are excited by light irradiation and thereby cooled as the gas flows through a mirrored cooling cell. In a closed loop embodiment, the gas then flows by means of a fan or compressor to a first heat exchanger where heat from the matter being cooled is transferred to the gas; and, then to a second heat exchanger where heat is transferred from the gas to a heat sink. The apparatus may be used either like a heat pump or air conditioner. In an open-end cooling apparatus embodiment, the gas flows from the cooling cell, through the first heat exchanger, and to atmosphere. The light source may be a 10.6 micron laser; or a 9-11 micron electric arc, a hot filament or the Sun. Working gases comprise N2 and C02; exhaust gases of engines or fuel cells; and gases which comprise different molecular composition gases or different isotopic species of the same molecular composition gas.