Mass of helium-4 from cyclotron frequency ratios <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mmultiscripts><mml:mi>He</mml:mi><mml:none/><mml:mo>+</mml:mo><mml:mprescripts/><mml:none/><mml:mn>4</mml:mn></mml:mmultiscripts>

An accurate atomic mass of 4He (or the alpha particle) is required for deriving the atomic mass of the electron from proposed measurements of the ground-state g factor of 4He+. However, there is a six-standard deviation current values in the Atomic Mass Evaluation and CODATA tabulation of fundamental constants are based. By measuring the cyclotron frequency ratios of 4He+ to D+2 , and of 4He+ to H2D+, we find the mass of 4He to be 4.002 603 254 67(8) u, favoring the more recent value.