The discovery of
published in The
Physical Review on
New Year’s Day,
1932. Just seven
weeks later, James
of the neutron.
in low-temperature physics, NBS, was
charged with producing large quantities
of liquid deuterium to fuel the first test
explosion, at Enewetak Atoll on 1 November 1952. Ferdinand Brickwedde led the
NBS team that produced this fuel, and
thus, within 21 years, he was instrumental
both in the basic discovery of deuterium
and its most spectacular application.
Today, deuterium is at the heart of
thermonuclear research through its
fusion reaction with tritium to produce
helium, thus releasing copious quantities
of energy, both in hydrogen bombs and
in the magnetically confined plasmas of
tokamak reactors, such as the international ITER machine under construction in France. (Tritium is
a radioactive isotope with a half-life of about 12 years. Produced
by cosmic rays and nuclear fission, it has a relative abundance
with respect to hydrogen of about 1 part in 1016. There are
only about 7 kg of tritium in Earth’s environment at any given
time.) Deuterium provides the moderator in heavy-water fission
reactors to slow down the neutrons produced in the fission, so
as to produce a chain reaction. The nucleus of deuterium, which
consists of a single proton and neutron, is called the deuteron. It
is used extensively in nuclear physics research.
In optics, deuterium is used to produce lamps that provide
continua in the ultraviolet as background for absorption spectroscopy as well as for radiometric calibration of UV spectrometers. The spectrum is not a confluence of close lines. It
is a pure continuum formed by the decay of an upper, bound,
molecular state to an unbound lower state that dissociates.
The continuum is a superposition of the continua formed by
the decay of each of the vibrational levels in the upper state to
the dissociating lower state. For deuterium, which is heavier
than hydrogen, both the vibrational and rotational levels
in the bound states are much more closely spaced than in
hydrogen, and the continuum is thus much stronger. Hence,
deuterium is preferred to hydrogen for use in commercial
primordial ratio. The ratio measured in comets is similar to that on Earth—which leads
to the speculation that the Earth’s surface
water may have originated in comets.
The question of measuring the true
primordial D/H ratio is closely related to
current questions regarding dark matter and
dark energy. It is known from the cosmic
microwave background that the fraction
of all matter and energy in the universe
that can be attributed to ordinary baryonic
matter (protons and neutrons) is only about
Recently astronomers M. Fumagalli, J.M. O’Meara and
J.X. Prochaska used the 10-m Keck I telescope to observe light
absorption from a quasar by an intergalactic cloud. Those obser-
vations have shown that this cloud contains almost no elements
heavier than lithium, and can thus be considered to be uncon-
taminated. From the intensities of absorption line of D in this
cloud, the D/H abundance ratio is determined as 20± 5 atoms
of D per million atoms of H. According to the authors, “The
detection of deuterium in one system at the level predicted by
primordial nucleosynthesis provides a direct confirmation of the
standard cosmological model.”
There will no doubt be much more science news regarding
the applications of deuterium. It is a pleasure for us to note
that both its initial discovery and its contributions to cosmology
reported 80 years hence are both the results of atomic spectros-
copy. Better living through … optics! t
Charles W. Clark ( firstname.lastname@example.org) is with the Joint Quantum Institute of the National Institute of Standards and Technology and the
University of Maryland, U.S.A. Joseph Reader is with the Physical
Measurement Laboratory of the National Institute of Standards and Technology in Gaithersburg, Md.
Deuterium and the origin of the universe
[ References and Resources ]
>> H.C. Urey et al. Phys. Rev. 39, 164 (1932).
>> H.C. Urey et al. Phys. Rev. 40, 1 (1932).
>> G.H. Herzberg. Spectra of Diatomic Molecules, Van Nostrand (1950).
>> “Moon-Struck Scientist, Harold Clayton Urey,” New York Times,
27 April 1961.
>> F.G. Brickwedde. Physics Today, September 1982, p. 34.
>> A.G. Truscott et al. Science 291, 2570 (2001).
>> R.L. Kurucz et al. Solar Flux Atlas from 296 to 1300 nm, Nat. Solar
Obser. Atlas No. 1 (1984).
>> G. Nave et al. Physica. Scripta T119, 35 (2005).
>> M. Fumagalli et al. Science 334, 1245 (2011).