On the evening of Feb. 1, Dr. Peter B. Polatin, a Washington psychiatrist, received a telephone call at his home from a man whose voice he did not recognize but who said he, too, was a doctor and had met Polatin in Los Angeles. The caller suggested lunch the next day and mentioned that he might have a job opportunity for Polatin.

They met at noon, at 19th and E streets NW, as the caller had suggested, and then drove in Polatin's car to the northwest area of the Ellipse, Polatin parked the car and started to get out when the man jumped to the back seat and placed a knife at the doctor's throat.

It was a violent start to a bizarre chain of events that led to the discovery that Polatin's companion had allegedly impersonated the Washington doctor in at least one California hospital, according to an affidavit in support of the man's arrest filed in D.C. Superior Court.

The man, Carmi Bar-Ilan, 38, who lives in Beverly Hills, was arrested Feb. 17 at Patton State Hospital, 70 miles south of Los Angeles, where he was listed on the staff as Dr. Peter B. Polatin, 35, according to Sgt. Jimmy W. Grayson, of the Los Angeles police department's robbery and homicide squad.

According to the affidavit, the man had once applied for unemployment compensation, listing Polatin as his employer.

According to U.S. Park Police, who investigated the case in Washington, Bar-Ilan has been charged here with assault with intent to kill. The incident at the Ellipse and the investigation that followed is laid out in unusual detail in the three-page affidavit.

It states that after the man put the knife to Polatin's throat, he said "not to worry" and added that two FBI agents were expected to join them.

The man then used tape to bind Polatin's hands and cover his mouth, took Polatin's wallet, taped over his nose and then started to choke him, first with the doctor's scarf and then with his hands, according to the affidavit. The affidavit does not specify precisely where the incident occurred, but the Ellipse is directly behind the White House in a heavily patrolled area.

According to the document, Polatin said he was able to break the tape that held his hands and began to scuffle with his assailant.

Polatin fled from the car, according to the affidvit, and ran to a jogger the U.S. Treasury building, where park police were called, according to court records.

Later, Polatin said the voice of his assailant resembled that of a man who had called him in Los Angeles several months ago about a job, the affidavit said. Polatin, who could not be reached for comment, was a psychiatric resident at the University of California at Los Angeles from 1974 to 1977, according to the Medical Society of the District of Columbia.

Polatin also remembered that the telephone caller had mentioned the Kedren clinic in California. It was there that Sgt. Grayson, of the Los Angeles force, began his search for the assailant.

Armed with a drawing of the man Polatin had described, Grayson said he went to the Kedren Community Mental Health Service, which he said is a psychiatric clinic.

When two aides there saw the drawing, Grayson said they remarked, "Oh, that's Dr. Carmi Bar-Ilan . . . What do you want him for?"

According to the affidavit, Bar-Ilan no longer worked at the hospital, and Grayson discovered that he was not licensed to practice medicine in California.

Grayson also discovered documents that showed Bar-Ilan had filed for unemployment compensation after he left Kedren, listing his employer as Dr. Peter Poletin, of the Patton State Hospital in California, according to the affidavit.

Polatin, meanwhile, received a check from Blue Shield of California for treatment of a man there in December, the affidavit said. On a document with the check, the patient's name appeared as Bar-Ilan and listed a Beverly Hills address. According to the affidavit, Polatin said he never treated the man and was not in California at the time.

Grayson said he drove to Patton Hospital on Feb. 17, armed with the Washington arrest warrant, only to be told that Bar-Ilan had taken the day off to go to UCLA. Grayson said he went to UCLA and also to Bar-Ilan's home, which Grayson described as a "very nice" two-story structure in a well-to-do neighborhood.

Late that afternoon, Grayson said he got a call from the security office at Patton Hospital.

"Your doctor has shown up on the premises," Grayson quoted the caller.