The CCL-K11 ongoing key comparison. Final report for the year 2012

Lasers from four national metrological institutes (NMIs) were compared in 2012 as part of the CCL-K11 ongoing key comparison, initiated by the 13th meeting of the Comite Consultative des Longuers (CCL) in 2007. The absolute frequency of R(127) 11-5 transitions of molecular iodine was measured for these lasers following the technical protocol for CCL-K11. The results of these measurements are compiled in this report. The comparison reports, as communicated by each participant, are included as appendices. This document constitutes the fourth final report for the ongoing key comparison CCL-K11.