Nuclear radius parameters (r0) for even-even nuclei from alpha decay

The decay data for 186 even-even alpha emitters have been analyzed, and used as input in the ALPHAD code to extract nuclear radius parameters (r0) for the daughter nuclides. The ALPHAD code employs Preston's spin-independent formalism to calculate alpha decay probabilities. A suite of databases available at the website of the National Nuclear Data Center (NNDC), Brookhaven National Laboratory was consulted to ensure the completeness and reliability of available experimental data pertaining to alpha decays of all the even-even nuclides in the entire nuclear landscape. The literature available up to June 2020 has been consulted. In addition to updating Qα values, half-lives, and other relevant quantities for all the even-even alpha emitters, 26 new even-even alpha emitters, and 164 references published since 1997, mostly in primary nuclear physics journals, have been added to the previous evaluation by Y.A. Akovali [1] in 1998, with a literature cutoff date of January 1997. We also present systematics of r0 parameters for even-even nuclides, and find that the radius parameters in an isotopic chain exhibit a regular pattern as a function of parent neutron number, showing a minimum at major closed shells, e.g. at N=126, increasing sharply above the closed shells, followed by a smoothly decreasing trend towards the next shell closure. The r0 parameters for even-even nuclides can be used as input parameters to calculate hindrance factors for the alpha decay of odd-A and odd-odd nuclides. We have also modified the original ALPHAD code so that the r0 parameters for the odd-A and the odd-odd nuclei can be automatically calculated using the present data file for r0 parameters of even-even daughter nuclides.