What happens to arsenic vapor molecules as their temperature increases?

In its vapor state, arsenic exists as ${\text{As}}_4$ molecules. As the temperature of this vapor increases, the following changes occur:

• Dissociation begins: The ${\text{As}}_4$ molecules remain stable until the temperature reaches approximately 800 °C, at which point they begin to dissociate.1
• Complete dissociation: As the temperature continues to rise, the dissociation process progresses until it is complete at about 1,700 °C, at which point the vapor consists of ${\text{As}}_2$ molecules.1