High-precision Penning trap mass measurements of 37,38Ca and their contributions to conserved vector current and isobaric mass multiplet equation

Penning trap mass measurements of the super-allowed β emitter 38Ca and of 37Ca have been performed using the low-energy beam and ion trap facility at the coupled cyclotron facility of the National Superconducting Cyclotron Laboratory. Both isotopes were produced by fast-beam fragmentation and in-flight separation. The mass of 38Ca (T1/2=440 ms) was determined with a precision of δm=280 eV, corresponding to a relative mass uncertainty of δm/m≅8x10-9. A mass excess value of ME =-22508.52(28) was obtained. 38Ca is a 0+→0+ emitter, and the improved mass value makes it a new candidate for testing the conserved vector current hypothesis. For 37Ca (T1/2=180 ms), a mass excess value of ME =-13135.7(1.4) was measured. Using the quadratic form of the isobaric mass multiplet equation and the improved 37Ca mass value, a precise prediction of the excitation energy of the 37Ar isobaric analog state was obtained