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MOLECULAR-DYNAMICS-NEWS  November 2007

MOLECULAR-DYNAMICS-NEWS November 2007

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Subject:

PhD position on "Precision Measurements on Cold Molecules in a Fountain" at Laser Centre Vrije Universiteit in Amsterdam

From:

Bethlem R <[log in to unmask]>

Reply-To:

Bethlem R <[log in to unmask]>

Date:

Fri, 9 Nov 2007 17:01:51 +0100

Content-Type:

TEXT/PLAIN

Parts/Attachments:

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TEXT/PLAIN (65 lines)

In the Atomic, Molecular and Laser Physics Group of the Laser Centre Vrije
Universiteit in Amsterdam a position for a PhD-student is available on the
following project:

Precision Measurements on Cold Molecules in a Fountain

The ability to manipulate neutral molecules using inhomogeneous electric
fields offers new possibilities for precision measurements. At LCVU, we
are building a molecular fountain. In this fountain, the first of its
kind, polar molecules are decelerated, cooled, and subsequently launched
upwards some 10-50 cm before falling back under gravity, thereby passing a
microwave cavity or laser beam twice - as they fly up and as they fall
back down. The effective interrogation time in such a Ramsey type
measurement scheme includes the entire flight time between the two
traversals through the driving field, which can be up to a second. This
long interrogation time will allow for extreme precision measurements on
molecular structure to a level at which fundamental physics theories can
be tested.

We plan to use the inversion frequency in ammonia around 23 GHz as a test
case. This measurement may be used as a test of the time-variation of
fundamental constants - an issue that has profound implications on how we
understand the universe. The inversion frequency in ammonia is determined
by the tunneling rate of the protons through the barrier between the two
equivalent configurations of the molecule, and is exponentially dependent
on the proton mass. By monitoring the inversion frequency over a period of
a few years, a possible variation of the proton-electron mass ratio can be
constrained or measured.

The vertical molecular beam decelerator for producing a slow beam of
ammonia molecules is fully operational. We are currently implementing an
electric quadrupole lens system to focus the beam into the microwave
cavity. The successful applicant will test and optimize this system and
will perform first measurements on molecules in the fountain.

The PhD student may start immediately, and will be funded for four years.

For more information about this project see:

www.few.vu.nl/~rick/

The Laser Centre Vrije Universiteit

At the Laser Centre Vrije Universiteit the research activities of several
groups from different disciplines in Physics, Chemistry, and Biology are
concentrated. The Atomic, Molecular and Laser Physics, headed by prof. W.
Ubachs, performs experiments ranging from high-resolution spectroscopy of
atoms and molecules, the study of ultra cold atoms and the development of
femto-second laser based frequency combs. Details on the activities of the
group can be found at:

www.nat.vu.nl/en/sec/atom/

Please send applications, preferably by e-mail, to:

Hendrick L. Bethlem
Laser Centre Vrije Universiteit
De Boelelaan 1081
1081 HV Amsterdam
The Netherlands
Tel.:      (+31) 20 598 7951
E-mail:    [log in to unmask]

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