Improved apparatus for trapped radical and other studies down to 1.5 K.
This note describes a Dewar system and associated apparatus for trapped free radical and other studies at temperatures down to 1.5 K. Cylindrical and rectangular microwave cavities can be used.
AN OPTICAL CELL FOR USE WITH LIQUID HELIUM
A low temperature cell is described that permits spectral absorption and emission measurements, as well as high energy irradiation of materials held at liquid helium temperatures. The liquid helium capacity of one liter is sufficient for up to 24 hours of continuous operation. Any substance whether it be solid, liquid, or gas at room temperatures can be studied. The all‐metal cell is entirely portable and can be employed with a number of instruments without modification. A sylphon bellows arrangement permits vertical displacement within the cell of the samples under study.
A low temperature infra-red transmission cell.
A versatile apparatus is described which allows the infra-red absorption spectra of materials to be obtained at temperatures down to that of liquid helium 4.2°K. The observed spectrum is the usual transmission measurement obtained in the normal way without disturbing the optics of the spectrometer.Samples can be observed which are solid, liquid, or gas at ordinary temperatures. Solids and liquids are suitably supported and are surrounded by helium gas at the temperature of liquid helium in order to provide for heat removal from the sample by both gaseous conduction and convection. The temperature rise of the sample due to absorbed radiation is thus very small. Condensible gases may be deposited onto one side of the vacuum tight infra-red transparent windows bathed on the inner side by cold helium gas. Observations have been made for periods of forty-five minutes using a single charge of approximately 200 cc of liquid helium. Detailed features of construction and operation conform to the exacting requirements of very low temperature work.