New branch:
Catalyzer -> Plasma Destabilizer -> Plasma Burster -> Star Exploder
This branch will deal Neutral/Elemental damage.
Basic Attack: fires a very quick rays of energy (looks like cold-blue colored Antigua's bullets) up to 9 squares, allowing up to 3 shots before reload. Bullets from this gun can set off explosive charges applied by Charge Attack (see below) or bullets from Pulsar series guns. When ray hit explosive charge or Pulsar gun series bullet, it explodes with triple strength.
Charge Attack: fires a very slow moving, exploding energy orb that has a range of 9 squares. When this orb touches enemy, orb explodes and deals good AoE damage. But when it hit with ray, the explosion will become two times wider and three times stronger.
What do you think about it?
Almost always when branching a weapon the only thing that changes is the damage type and/or status affliction. The branches also are fairly equal at the same star ranks, such as Glacius and Combuster; they are not necessarily the same, but equal other than the status afflicted by the explosions in the charge for either sword.
The basic attack not only fires very far but also detonates both Catalyzer and Pulsar bullets, the latter detonating upon contact to a target on its own. Having it fire quick bullets (assumed to match Antigua based on your context) automatically makes it overpower other Catalyzer lines on the basic attack. Having split normal-element also makes it more powerful. Its range is enormous and would outclass Antigua for flick tactics.
The charge attack is essentially the Pulsar charge with the same unnecessarily long bullet path with an even more overpowered detonation mechanic. Unless this weapon has less than half the base damage of Catalyzer it would be significantly overpowered in every way and make Catalyzer less viable than it already is.