Action to be taken when a sub-ordinate defames the controlling officer by providng false information

I am working in the senior management position in a Govt of India organization. Two days back one of the junior employee mailed, from the office mail after office hours, to the highest authority of the organisation about series of lies about me and entangled IIT professor and student by doubting their admission procedure and abused the students who is in 3rd year PhD. The accused employee does not related to the IIT professor and students anyway. I believe that the unsubstantiated allegation has been made with a malafide intention to defame me, IIT Professor and the student working under joint supervision. Based on the entire complaint these points emerged. • Violated the conduct rules (26-E) being a government servant • Wilfully disseminated false information • Insulted the centre and the individuals of the centre • Doubted the integrity of the centre • Wrong information provided related to COVID 19 protocols • Spoiled the peaceful working environment and indulging unlawful activities of the other staff. • Defamation of 3 persons at a time • Questioning and doubting the selection procedure of other organization • Spreading hatred • False intimidation He has troubled many of the scientists in other centres and the records are available with the earlier centres. Seek your advice how to go about as I am working in a Government of India organization