When you cool a gas, how does this affect the de Broglie wavelength of the gas atoms? When you cool a gas, how does this affect the de Broglie wavelength of the gas atoms? Being cooled, the gas atoms slow down so that their de Broglie wavelength will increase. Being cooled, the gas atoms slow down so that their de Broglie wavelength will decrease. The de Broglie wavelength will remain the same because it does not depend on temperature.