Shares of Cymer Inc., the San Diego maker of laser equipment used in the manufacture of semiconductors, rocketed up by more than $24 or about 51 percent in midday Oct. 17 trading on the Nasdaq exchange to above $71 following news that the company agreed to be acquired by ASML Holding NV, a Dutch company that is Cymer’s biggest customer, for 1.95 billion euros or about $2.5 billion.

Boards of directors from both companies approved the transaction that calls for ASML to pay $20 in cash and 1.15 shares of ASML stock for each share of Cymer. Shares of ASML closed at $53.59 on Oct. 16. The total price reflects a premium of 61 percent over Cymer’s average stock price over the past 30 days, the companies said.

ASML said it intends to manage Cymer’s commercial operations as an independent division in the United States. Cymer is the region’s 17th largest company based on revenue, with 2011 sales at $594 million. It has about 1,100 employees, most of which work at the headquarters office in Rancho Bernardo.

The transaction is expected to close in the first half of 2013, subject to approvals from international regulators and Cymer’s shareholders.