Naturally occurring titanium (22Ti) is composed of five stable isotopes; 46Ti, 47Ti, 48Ti, 49Ti and 50Ti with 48Ti being the most abundant (73.8% natural abundance). Twenty-one radioisotopes have been characterized, with the most stable being 44Ti with a half-life of 59.1 years, 45Ti with a half-life of 184.8 minutes, 51Ti with a half-life of 5.76 minutes, and 52Ti with a half-life of 1.7 minutes. All of the remaining radioactive isotopes have half-lives that are less than 33 seconds, and the majority of these have half-lives that are less than half a second.
The isotopes of titanium range from 39Ti to 64Ti. The primary decay mode for isotopes lighter than the stable isotopes is β+ and the primary mode for the heavier ones is β−; the decay products are respectively scandium isotopes and vanadium isotopes.
There are two odd stable isotopes of titanium (47Ti and 49Ti), which thus have non-zero nuclear spin of 5/2− and 7/2− (respectively) and are NMR-active.[4]
^( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
^# – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
^ ab# – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
^Bold symbol as daughter – Daughter product is stable.
^( ) spin value – Indicates spin with weak assignment arguments.
Titanium-44
Titanium-44 (44Ti) is a radioactive isotope of titanium that undergoes electron capture with a half-life of 59.1 years to an excited state of scandium-44, before reaching the ground state of 44Sc and ultimately of 44Ca.[6] Because titanium-44 can decay only through electron capture, its half-life increases slowly with its ionization state and it becomes stable in its fully ionized state (that is, having a charge of +22),[7] though as astrophysical environments never lack electrons completely will always decay.
Titanium-44 is produced in relative abundance in the alpha process in stellar nucleosynthesis and the early stages of supernova explosions.[8] It is produced when stable calcium-40 adds an alpha particle (helium-4), as nickel-56 is the result of adding three more. The age of supernova remnants (even though nickel-56 has died away to iron) may be determined through measurements of gamma-ray emissions from the relatively long-lived titanium-44 and of its abundance.[7] It was observed in the Cassiopeia A supernova remnant and SN 1987A at a relatively high concentration, enhanced by the delayed decay in the ionizing conditions.[6]
^Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
^ abMochizuki, Y.; Takahashi, K.; Janka, H.-Th.; Hillebrandt, W.; Diehl, R. (2008). "Titanium-44: Its effective decay rate in young supernova remnants, and its abundance in Cas A". Astronomy and Astrophysics. 346 (3): 831–842. arXiv:astro-ph/9904378.
^Fryer, C.; Dimonte, G.; Ellinger, E.; Hungerford, A.; Kares, B.; Magkotsios, G.; Rockefeller, G.; Timmes, F.; Woodward, P.; Young, P. (2011). Nucleosynthesis in the Universe, Understanding 44Ti(PDF). ADTSC Science Highlights (Report). Los Alamos National Laboratory. pp. 42–43.
