EXHIBIT 99.1

[LOGO] mks
Technology for Productivity

                                                           FOR IMMEDIATE RELEASE

                                                     INVESTOR RELATIONS CONTACT:
                                                                  Ronald Weigner
                                        Vice President & Chief Financial Officer
                                                           MKS Instruments, Inc.
                                                                    978.975.2350

                MKS INSTRUMENTS ACQUIRES ENI DIVISION OF EMERSON

     February 1, 2002, Andover, Mass.-- MKS Instruments, Inc. (NASDAQ: MKSI), a
leading supplier of gas measurement, control and analysis products used in
semiconductor and other advanced thin-film manufacturing processes, today
announced the closing of its acquisition of the ENI Division of Emerson (NYSE:
EMR). ENI is a leading supplier of solid-state radio frequency (RF) and direct
current (DC) plasma power supplies, matching networks and instrumentation to the
semiconductor and thin-film processing industries. Combined revenues of the two
companies totaled approximately $490 million for the twelve months ended
September 30, 2001.

     "This acquisition expands our comprehensive suite of products, and
exemplifies our strategy to acquire and leverage technologies that surround the
manufacturing process chamber. Specifically, it enables MKS to offer higher
value and more highly integrated application solutions to our global customer
base by combining ENI's solid-state power conversion technology with MKS' core
competency in plasma management," said John Bertucci, Chairman, Chief Executive
Officer and President of MKS.

     The transaction involved the exchange of 12 million shares of MKS common
stock for the businesses and assets of ENI. Based in Rochester, New York, ENI
has R&D, engineering and manufacturing operations in the United States and Asia
and a worldwide sales and service organization.

     At the close of the transaction, Emerson president James Berges joined the
MKS Board of Directors.

     ENI products will become part of a technologically advanced product family
that includes MKS' pressure management subsystems, vacuum subsystem products,
advanced materials delivery products, process monitor products, digital process
control network products, plasma and reactive gas generator products, and
infrared-based gas and thin-film measurement products.

     For information on MKS, visit WWW.MKSINST.COM.



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     MKS Instruments, Inc. is a leading worldwide developer, manufacturer and
supplier of instruments, components and subsystems used to measure, control, and
analyze gases in semiconductor manufacturing and similar industrial
manufacturing processes and a leading developer, manufacturer and supplier of
reactive gas generation and power delivery products. MKS Instruments, Inc. sold
products to more than 4,000 customers in 2001. In addition to semiconductors,
MKS' products are used in processes to manufacture a diverse range of products,
such as optical filters, fiber optic cables, flat panel displays, magnetic and
optical storage media, medical equipment, architectural glass, solar panels and
gas lasers.

     Statements in this press release including those regarding the benefits of
the business combination transaction and future financial and operating results
are forward-looking statements within the meaning of the "safe harbor"
provisions of the Private Securities Litigation Reform Act of 1995. These
statements are based on management's current expectations or beliefs and are
subject to a number of factors and uncertainties that could cause actual results
to differ materially from those described in the forward-looking statements. The
following important factors, among others, could cause actual results to differ
materially from those described in the forward-looking statements: costs related
to the transaction; the difficulty the market may have in valuing the MKS/ENI
business model; the risk that MKS' and ENI's businesses will not be integrated
successfully; the failure of the combined business to realize anticipated
benefits of the transaction; and other economic, business, competitive and/or
regulatory factors affecting MKS' business generally, including those factors
set forth in the company's filings with the Commission, including the most
recent Annual Report on Form 10-K and Quarterly Report on Form 10-Q. MKS is
under no obligation to, and expressly disclaims any obligation to, update or
alter its forward-looking statements, whether as a result of new information,
future events or otherwise.

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