Though agenda is set, there's always the question of chemistry

``There's a certain chemistry that takes place when the President and Gorbachev meet,'' says Max Kampelman, head of the United States nuclear arms control negotiating team and one of the participants in next week's summit meeting. No matter how much staff work is done, how many briefing papers are written, and how carefully planned the meetings, says Mr. Kampelman, there is an element of unpredictability that gives summits a character and life of their own.

That will undoubtedly be true when President Ronald Wilson Reagan and Soviet leader Mikhail Sergeyevich Gorbachev meet here in Washington tomorrow.

The agenda has been thoroughly prepared in advance. The logistical arrangements - right down to the memo pads and the drinking glasses on the tables - are largely in place. The US government is even going to snatch Soviet domestic television broadcasts from a satellite, so that Mr. Gorbachev will be able to see how the summit is being played back home.

What neither side can prepare for, however, is the chemistry.

It will come into play almost as soon as Mr. Reagan greets the Soviet leader at the White House tomorrow. Over the next two days, the two leaders will cover an agenda that defines the superpower relationship - and shapes its future course.

It is a formula that is, by now, rote: arms control, human rights, bilateral relations, and regional conflicts. The two men will devote one meeting to each of the topics, interspersed with dinners, and then convene for a fifth and final wrap-up session on Thursday.

As a practical matter, however, a senior administration official says that although the entire agenda will be covered, the primary focus will be on nuclear arms control.

Gorbachev will be invited, during the first face-to-face meeting with Reagan tomorrow, to review US-Soviet relations. It is expected that the Soviet Communist Party general secretary will give a general presentation on all the topics to be discussed, and then focus on the latest Soviet nuclear disarmament proposals.

US and Soviet officials are then expected to form small ``working groups'' to discuss each of the four main topics on the agenda, searching for areas of accord that can be translated into formal statements or agreements.

The working group on arms control will be the primary focus of attention. The delegations will be headed by presidential adviser Paul Nitze on the US side and military chief of staff Sergei Akhromeyev on the Soviet side.

Gen. Nikolai Chervov, a Soviet military arms control specialist, says the Soviets will be presenting new proposals during the summit. Kampelman says the US is prepared to study any proposal carefully, and US experts throughout the government are ready to provide quick analysis and reaction.

Meanwhile, tomorrow afternoon, Reagan and Gorbachev will sign the agreement banning US and Soviet intermediate-range nuclear missiles (INF). The agreement contains some of the most extensive verification provisions ever, including on-site inspections on both US and Soviet territory. Some conservatives, however, have expressed concerns that it does not go far enough. Both the President and the Soviet leader will probably use the summit to plug for ratification of the treaty in the US Senate.

US Secretary of State George Shultz and Soviet Foreign Minister Eduard Shevardnadze will be present for some of the meetings between Reagan and Gorbachev, but will also likely have separate meetings, in addition to supervising the working groups.

When Gorbachev is not involved in the formal summit sessions, he will be meeting with US senators and congressmen, businessmen, and a wide variety of other public figures. In addition, he will hold a press conference at the end of the summit that will doubtless be telecast worldwide.

In fact, the summit, will be a test of the public relations skills of the two leaders. Both governments have already held rounds of briefings, press conferences, and meetings with reporters to get their viewpoints across.

Tomorrow afternoon, Reagan and Gorbachev will broadcast messages to the US and Soviet public from the White House state dining room.

In the evening, there will be a state dinner in Gorbachev's honor, and Wednesday evening Gorbachev and his wife, Raisa, will play host to the President and Mrs. Reagan at the Soviet Embassy, just blocks from the White House.

Against this glittery backdrop, the substantive work of the summit will be taking place in conference rooms in and around the White House.

Arms control. Marshal Akhromeyev and Mr. Nitze will be exploring the thorny questions of how to achieve reductions in strategic nuclear arms. There is already a draft agreement that US and Soviet negotiators will be bringing with them from Geneva.

Among the more difficult issues: whether reductions in long-range nuclear weapons can take place at the same time the US presses ahead with plans for a space-based missile defense system, known as the Strategic Defense Initiative.

Regional issues. The two sides will engage in a review of the world's trouble spots and potential areas of superpower conflict. Afghanistan - and the possibility of a Soviet troop withdrawal from the country - is expected to receive the lion's share of attention. The two delegations will also discuss the Gulf war, the Middle East, Vietnam and Cambodia, Central America, and southern Africa.

US officials say they are hopeful on progress toward setting a deadline for a Soviet pullout from Afghanistan. No other substantive agreements are expected, however.

Human rights. The US will press for more emigration from the Soviet Union, especially of Soviet Jews. Although American officials are pleased that emigration is higher than last year, they still says the number of exit visas granted is well below the demand.

The US will also present lists of divided spouses, dual citizenship cases, and ``blocked marriages'' (in which the Soviet Union is preventing a marriage between a Soviet citizen and an American). US diplomats will ask about planned revisions in the Soviet criminal code dealing with religious and human rights activists and other forms of dissent.

Bilateral relations. A grab bag of issues - ranging from maritime agreements to scientific and technical exchanges to the status of the US Embassy in Moscow - will be discussed.

The US does not expect to conclude agreements for new consulates in the two countries. And the State Department is studying what to do with its nearly completed embassy in Moscow, which it has found to be riddled with Soviet listening devices. American diplomats do not expect the issue to be resolved during the summit.

There is the possibility, according to a senior American official, of two agreements involving scientific exchanges.

And at least two major commercial agreements are expected to be announced during the summit.

But American officials repeatedly stress that, during summits, the unexpected is all but expected - that is, the two leaders can stray from the prepared agenda at will, with unexpected results.

US officials say privately that they are confident the President is unlikely to engage in the kind of free-wheeling discussions that he had with Gorbachev at the Iceland summit last year. Then, the two men discussed an agreement to eliminate virtually all nuclear weapons.

But the President says he is hopeful that this summit can lay the foundation for ``a gigantic step forward'' - the halving of each side's nuclear arsenals.

``He believes it's possible,'' one US official says.

And, a Soviet diplomat adds, Gorbachev does, too.