Phase space factors for β+β+ decay and competing modes of double- β decay

A complete and improved calculation of phase space factors (PSF) for $2\ensuremath{\nu}{\ensuremath{\beta}}^{+}{\ensuremath{\beta}}^{+}$ and $0\ensuremath{\nu}{\ensuremath{\beta}}^{+}{\ensuremath{\beta}}^{+}$ decay, as well as for the competing modes $2\ensuremath{\nu}\mathrm{EC}{\ensuremath{\beta}}^{+}$, $0\ensuremath{\nu}\mathrm{EC}{\ensuremath{\beta}}^{+}$, and $2\ensuremath{\nu}\mathrm{ECEC}$, is presented. The calculation makes use of exact Dirac wave functions with finite nuclear size and electron screening and includes life-times, single and summed positron spectra, and angular positron correlations.