DICTIONARY OF GEOPHYSICS, ASTROPHYSICS, and ASTRONOMY

Lyman series
ionize hydrogen from the ground state. Thus,
hydrogen is opaque to radiation of wavelength
shorter than the Lyman limit. There are corresponding
limits associated with transitions from
the second, third, fourth, fifth ... excited states,
called the Balmer, Paschen, Brackett, Pfund ...
limits.
Lyman series The set of spectral lines in the
far ultraviolet region of the hydrogen spectrum
with frequency obeying
ν = cR∞
1/n 2 f − 1/n2 i
,
where c is the speed of light, R∞ is the Rydberg
constant, and nf and ni are the final and
initial quantum numbers of the electron orbits,
with nf = 1 defining the frequencies of the
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spectral lines in the Lyman series. This frequency
is associated with the energy differences
of states in the hydrogen atom with different
quantum numbers via ν = E/h, where h is
Planck’s constant, and where the energy levels
of the hydrogen atom are:
En = hcR∞/n 2 .
Lysithea Moon of Jupiter, also designated
JX. Discovered by S. Nicholson in 1938, its orbit
has an eccentricity of 0.107, an inclination of
29.02 ◦ , and a semimajor axis of 1.172×10 7 km.
Its radius is approximately 18 km, its mass,
7.77 × 10 16 kg, and its density 3.2 g cm −3 . Its
geometric albedo has not been well determined,
and it orbits Jupiter once every 259.2 Earth days.