Rubidium
Applications

Rubidium compounds are sometimes used in fireworks to give them a purple color. Rubidium has also been considered for use in a thermoelectric generator using the magnetohydrodynamic principle, whereby hot rubidium ions are passed through a magnetic field. These conduct electricity and act like an armature of a generator, thereby generating an electric current. Rubidium, particularly vaporized Rb, is one of the most commonly used atomic species employed for laser cooling and Bose–Einstein condensation. Its desirable features for this application include the ready availability of inexpensive diode laser light at the relevant wavelength and the moderate temperatures required to obtain substantial vapor pressures. For cold-atom applications requiring tunable interactions, Rb is preferred for its rich Feshbach spectrum.

Rubidium has been used for polarizing He, producing volumes of magnetized He gas, with the nuclear spins aligned rather than random. Rubidium vapor is optically pumped by a laser, and the polarized Rb polarizes He through the hyperfine interaction. Such spin-polarized He cells are useful for neutron polarization measurements and for producing polarized neutron beams for other purposes.

The resonant element in atomic clocks utilizes the hyperfine structure of rubidium's energy levels, and rubidium is useful for high-precision timing. It is used as the main component of secondary frequency references (rubidium oscillators) in cell site transmitters and other electronic transmitting, networking, and test equipment. These rubidium standards are often used with GNSS to produce a "primary frequency standard" that has greater accuracy and is less expensive than caesium standards. Such rubidium standards are often mass-produced for the telecommunications industry.

Other potential or current uses of rubidium include a working fluid in vapor turbines, as a getter in vacuum tubes, and as a photocell component. Rubidium is also used as an ingredient in special types of glass, in the production of superoxide by burning in oxygen, in the study of potassium ion channels in biology, and as the vapor in atomic magnetometers. In particular, Rb is used with other alkali metals in the development of spin-exchange relaxation-free (SERF) magnetometers.

Rubidium-82 is used for positron emission tomography. Rubidium is very similar to potassium, and tissue with high potassium content will also accumulate the radioactive rubidium. One of the main uses is myocardial perfusion imaging. As a result of changes in the blood–brain barrier in brain tumors, rubidium collects more in brain tumors than normal brain tissue, allowing the use of radioisotope rubidium-82 in nuclear medicine to locate and image brain tumors. Rubidium-82 has a very short half-life of 76 seconds, and the production from decay of strontium-82 must be done close to the patient.

Rubidium was tested for the influence on manic depression and depression. Dialysis patients suffering from depression show a depletion in rubidium, and therefore a supplementation may help during depression. In some tests the rubidium was administered as rubidium chloride with up to 720 mg per day for 60 days.
detectable_format:constrained_response