His initial contributions to science came from his study of light bulbs (a continuation of his PhD work). His first major development was the improvement of the diffusion pump, which ultimately led to the invention of the high-vacuum rectifier and amplifier tubes. A year later, he and colleague Lewi Tonks discovered that the lifetime of a tungsten filament could be greatly lengthened by filling the bulb with an inert gas, such as argon, the critical factor (overlooked by other researchers) being the need for extreme cleanliness in all stages of the process. He also discovered that twisting the filament into a tight coil improved its efficiency. These were important developments in the history of the incandescent light bulb. His work in surface chemistry began at this point, when he discovered that molecular hydrogen introduced into a tungsten-filament bulb dissociated into atomic hydrogen and formed a layer one atom thick on the surface of the bulb.