(color online) Arrhenius plot for the reaction of . TST: presents the study using transition-state theory calculations; CVT/SCT: presents the study using canonical variational transition-state theory with small-curvature-tunneling (SCT) calculations; CUS/SCT: presents the study using canonical unified statistical theory with SCT calculations; RPMD(PES-2014): other study using ring polymer molecular dynamics approach calculations on PES-2014 from Ref. [33]; Exp.1: Experimental values from Ref. [31]; Exp.2: Experimental values from Ref. [30]. Arrhenius plot for the isotope effects on the rate constants. ³A′ presents the reaction path through SP^1st (³A′) from ^[47], ³A″ presents the reaction path through SP^1st (³A″).