Libyan leader Muammar Qaddafi sank into a severe depression after last week's U.S. bombing raid that wounded two of his sons and killed a 15-month-old girl described by Libyan officials as his adopted daughter, according to a reliable intelligence report reaching officials here.

Qaddafi has begun displaying the extravagant mood swings of a manic depressive, the sources said. Central Intelligence Agency specialists have concluded that the bombing raid, which apparently caught Qaddafi completely by surprise, triggered the depression. They said he was particularly affected by the wounding of the sons, one of whom remains in serious condition.

Meanwhile, there were some strong indications from sources yesterday that the United States is close to proving that Libya is responsible for the shooting last week of William J. Calkins, a U.S. Embassy communications specialist in Khartoum. Calkins was shot the day after the U.S. raid and a bullet inflicted a serious brain injury.

The U.S. Embassy in Sudan last week evacuated several hundred "nonessential" personnel and all dependents. For nearly a year there have been U.S. intelligence reports that Libya planned attacks on Americans and U.S. facilities in Sudan, sources said.

President Reagan and other officials have said that the United States will strike at Libya again if the Qaddafi-sponsored terrorism continues.

Qaddafi's depressed condition has kept his public profile low following the raid, according to the intelligence report. Although Qaddafi has appeared on Libyan television and has made several other appearances, he has been comparatively subdued.

His sluggish personal response seems to have somewhat delayed the Libyan reaction to last Tuesday's U.S. air strike in which more than 100 tons of bombs were dropped on five targets including his personal headquarters, called the Bab Azizzia or "Splendid Gate" barracks.

Members of Qaddafi's family were inside, and at least two of his young sons were wounded. Qaddafi's relationship to the dead 15-month-old girl is still not clear. Libyan officials have said she was his adopted daughter, although U.S. sources say they doubt this is true.

An intelligence source predicted that Qaddafi would soon cycle back into his familiar mold as a wild, outspoken leader, and in all likelihood will begin planning retaliation against the United States. "A lamb one day and a lion the next," said one well-placed source.

The psychological portrait of Qaddafi that emerges from reliable intelligence sources grows more bizarre. In 1982, a classified CIA profile of the Libyan leader concluded that he "is judged to suffer from a severe personality disturbance -- a 'borderline personality disorder.' " In simple terms that means he had periods of erratic behavior and judgment.

Qaddafi, according to reliable reports, also has used excessive amounts of sleeping pills and stimulants. Last month, Newsweek magazine reported that an updated CIA profile said Qaddafi was using hallucinogens, and that one source conferring with him during the Gulf of Sidra exercises last month found him "disoriented and incomprehensible."

The Libyan leader's psychological state may, according to U.S. sources, make it more difficult for the United States to assess its own policy and calculate its next step. As one source said, "The issue is what's next . . . . Everyone is waiting for the other shoe to drop. If the other guy [Qaddafi] is on something or wigged out, it's that much harder to do your own planning . . . . "

Reagan has on several occasions referred to Qaddafi's mental condition, calling him "flaky" and a "mad dog."

Libyan Ambassador to the United Nations Ali Treiki yesterday seemed to confirm that his country was surprised that the United States bombed what he considers nonmilitary targets. "We were not expecting that they will attack civilians," Treiki said. "We were ready to defend our military installations. But the problem, they came to the civilian targets, either in Benghazi or in Tripoli."

Treiki, a former Libyan foreign minister and longtime official in the Qaddafi regime, called for a U.N. investigation of the raid. He said a U.N. team would find that no Libyan military targets were hit. Apparently echoing Qaddafi's concern, Treiki said, "I can show, I have the picture of the children here with me, [some] died in their beds."

He did not get a chance to show the picture on U.S. television, where he was appearing on ABC's "This Week With David Brinkley."

Treiki also said that the Reagan administration's hope that the raid would trigger a coup against Qaddafi has not and will not be realized. "Contrary now," Treiki said, "Qaddafi is more stronger. He has the support not only of the Libyan people, but all Arab and Muslim world . . . . "

U.S. sources last week more or less agreed that the secondary goal of sparking an anti-Qaddafi uprising had not worked, and that the short-term result of the bombing raid might be more power and sympathy for the Libyan leader.

Appearing on NBC's "Meet the Press" yesterday, former Reagan national security affairs adviser Robert C. McFarlane seemed to agree, saying, "I think basically, Qaddafi's continuity is pretty much assured."