It's very dependent on scene scale, as different scales will require different Absorption amounts - there's no "one size fits all" so impossible to say which settings to use. Absorption is usually best close to but not quite white.
Most importantly here your Scattering is black - which means the volume won't scatter any light (which is what is happening in a volumetric set up - light is traveling in one direction, hits a dust particle in the air for example, and gets bounced to travel in another direction). With Absorption only and black scattering you are just creating a dark fog that will darken everything without scattering any light.
To make the rays stand out more, it's best to have Single Bounce Only checked, otherwise light may bounce multiple times giving the whole volume a brighter glow (which means the first bounce will stand out less since it will be surrounded by more of a glow).