Notwithstanding the six (6) year or less sentence limitation of this part, an especially mitigated offender, as defined by § 40-35-109, or a standard offender, as defined by § 40-35-105, who is convicted of a violation of § 39-17-417(a) with respect to a controlled substance in an amount less than that set out in § 39-17-417(i), is eligible for placement in the special alternative incarceration unit as defined and authorized by this part.