4Be + n → 2(4

2He) + 2n

Beryllium is also transparent to most wavelengths of X-rays and gamma rays, making it useful for the output windows of X-ray tubes and other such apparatus.

Also, beryllium is a good source for relatively-small numbers of free neutrons in the laboratory.

These are liberated when beryllium nuclei are struck by energetic alpha particles[3] producing this nuclear reaction:

4Be + 4

2He → 12

6C + n

where 4

2He is an alpha particle and 12

6C is a carbon-12 nucleus.[4]

[edit]Isotopes and nucleosynthesis

Main articles: Isotopes of beryllium and beryllium-10

Plot showing variations in solar activity, including variation in 10Be concentration.

Note that the beryllium scale is inverted, so increases on this scale indicate lower 10Be levels
9Be is the only stable isotope.