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                                                           FOR IMMEDIATE RELEASE

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

            MKS INSTRUMENTS ANNOUNCES DEFINITIVE AGREEMENT TO ACQUIRE
                          THE ENI DIVISION OF EMERSON


     COMBINATION CREATES BROAD SUBSYSTEM SUPPLIER TO THE SEMICONDUCTOR AND
                          THIN FILM EQUIPMENT INDUSTRY.

                   ADDS COMPLEMENTARY RF AND DC POWER DELIVERY
                  SUBSYSTEM PRODUCTS TO MKS' PRODUCT PORTFOLIO

         October 31, 2001, 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 that it has entered into a definitive agreement to acquire 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.
The acquisition further expands MKS' comprehensive suite of products and is part
of the Company's ongoing strategy to augment its product and technology
portfolio, and to provide higher added value subsystems for its key OEM and
end-user customers. ENI, based in Rochester, NY, is a global company that
employs more than 600 people worldwide. ENI has R&D, engineering and
manufacturing operations in the United States and Asia and a worldwide sales and
service organization.

         Under the terms of the agreement, MKS will issue 12 million shares of
common stock to Emerson in exchange for the businesses and assets of ENI. Based
on MKS' closing stock price on October 30, 2001 of $20.91, the transaction is
valued at $251 million. MKS will also assume approximately $3.5 million of net
debt. The Board of Directors of MKS has unanimously approved the transaction.
Completion of the acquisition is subject to customary closing conditions,
including the approval of MKS' shareholders. After the close of the transaction,
Emerson will own approximately 24 percent of MKS' outstanding stock, and Emerson
President James Berges will join the MKS Board of Directors. The transaction is
expected to be completed in the first calendar quarter of 2002 and is
anticipated to be accretive to MKS' cash earnings per share in 2002 without the
inclusion of synergies.

         ENI's 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 FTIR - based gas and thin-film measurement products.

         ENI's products complement the portfolio of MKS' ASTeX Products group,
the leading supplier of plasma and reactive gas solutions. The acquisition adds
critical solid-state power conversion technology to MKS' core capability in
plasma management, and enables MKS to offer more highly integrated and higher
performance products to its OEM and end-user customers. ENI will become the ENI
Products group of MKS. The operations of ENI Products will continue to be
managed by ENI's current President, Ed Maier, who will become Vice President and
General Manager, ENI Products, and will report to Dr. Peter Younger, President
and Chief Operating Officer of MKS.

         The transaction is consistent with MKS' objective of expanding its core
technologies and product offering through strategic acquisitions. MKS Chairman
and CEO John Bertucci said, "By combining ENI's strength in power delivery
subsystems and ASTeX's expertise in reactive gas generation and plasma
technology, we are confirming MKS' commitment to providing our customers with
application solutions for their leading edge products. Together, we will
increase our critical mass, broaden our technology base and strengthen our
ability to serve our customers."

         James Berges stated further, "We, at Emerson, are excited about this
strategic combination and look forward to remaining a long-term partner and
supporter of MKS. ENI is a power conversion company, but its focus on the
semiconductor capital equipment market is not mainstream to Emerson's Network
Power business. Nevertheless, we like the long term, through-the-cycle growth
characteristics of semiconductors, and see the combination of MKS and ENI as a
way to realize broader and deeper participation in this market."

         Management will host a conference call on Wednesday, October 31 at 8:00
a.m. (EST) to discuss the transaction. To participate on the audio portion of
the call, please dial 800-219-6110 (domestic) or 303-262-2130 (international) at
least five minutes before start time.

         For further information on ENI's products and technology, visit
www.enipower.com. For information on MKS and to view a presentation related to
the transaction, 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 2000. 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.

This report may contain projections or other forward-looking statements
regarding future events or the future financial performance of MKS. These
projections or statements are only predictions. Actual events or results may
differ materially from those in the projections or other forward-looking
statements set forth herein. Among the important factors that could cause actual
events to differ materially from those in the projections or other
forward-looking statements are the challenges and risks involved with
integrating the operations of MKS and ENI, potential fluctuations in quarterly
results, dependence on new product development, rapid technological and market
change, acquisition strategy, manufacturing and sourcing risks, volatility of
stock price, international operations, financial risk management, and future
growth subject to risks. Readers are referred to MKS' filings with the
Securities and Exchange Commission, including its most recent filings on Form
10-K and 10-Q, for a discussion of these and other important risk factors
concerning MKS and its operations.