When a molecule absorbs ir electromagnetic energy, what are the vibrational modes affected

Stretching vibration, and

Bending vibration (Rocking, wagging, Twisting and Scissoring)

Explanation:

Stretching vibration: this causes change in the length of a bondBending vibration: this causes change in the angle between two bonds

Bending vibration can occur as rocking, wagging, twisting and Scissoring vibration

2a) Rocking vibration: this causes change in angle between group of the atoms

2b) Wagging vibration: this causes change in angle between the plane of a group of atoms

2c) Twisting vibration: this causes change in the angle between the planes of two groups of atoms.

2d) Scissoring vibration: this causes the movement of two atoms toward and away from each other

Ch4 and ph3 are both covalent since they are composed both of non-metals.    ch4 is non- polar because of  london forces and has a geometry of tetrahedral  ph3 , on the other hand, is umbrella shaped polar and has dipole-dipole intermolecular force (imf) . since ph3 is polar, it has a stronger imf   

It must be measured in k.hope my answer is to you : )