236 research outputs found
Test of quantum chemistry in vibrationally-hot hydrogen molecules
Precision measurements are performed on highly excited vibrational quantum
states of molecular hydrogen. The rovibrational levels of H
(), lying only cm below the first dissociation
limit, were populated by photodissociation of HS and their level energies
were accurately determined by two-photon Doppler-free spectroscopy. A
comparison between the experimental results on level energies with the
best \textit{ab initio} calculations shows good agreement, where the present
experimental accuracy of cm is more precise than
theory, hence providing a gateway to further test theoretical advances in this
benchmark quantum system.Comment: 5 pages, 4 figures, and 2 table
B\,^1\Sigma^{+}_{u} and EF\,^{1}\Sigma^{+}_{g} level energies of D
Accurate absolute level energies of the B\,^1\Sigma^{+}_{u}, and
EF\,^{1}\Sigma^{+}_{g}, rovibrational quantum states of molecular
deuterium are derived by combining results from a Doppler-free two-photon laser
excitation study on several lines in the
(0,0) band, with results
from a Fourier-transform spectroscopic emission study on a low-pressure
hydrogen discharge. Level energy uncertainties as low as 0.0005 cm are
obtained for some low-lying E\,^{1}\Sigma^{+}_{g} inner-well rovibrational
levels, while uncertainties for higher-lying rovibrational levels and those of
the F\,^{1}\Sigma^{+}_{g} outer-well states are nominally 0.005 cm.
Level energies of B\,^1\Sigma^{+}_{u} rovibrational levels, for
and are determined at an accuracy of 0.001 cm. Computed
wavelengths of D Lyman transitions in the
B\,^1\Sigma^{+}_{u}-X\,^{1}\Sigma^{+}_{g} () bands are also tabulated
for future applications.Comment: appears in Journal of Molecular Spectroscopy (2014
High-precision laser spectroscopy of the CO A - X (2,0), (3,0) and (4,0) bands
High-precision two-photon Doppler-free frequency measurements have been
performed on the CO A - X fourth-positive system (2,0),
(3,0), and (4,0) bands. Absolute frequencies of forty-three transitions, for
rotational quantum numbers up to , have been determined at an accuracy
of cm, using advanced techniques of two-color 2+1'
resonance-enhanced multi-photon ionization, Sagnac interferometry,
frequency-chirp analysis on the laser pulses, and correction for AC-Stark
shifts. The accurate transition frequencies of the CO A - X
system are of relevance for comparison with astronomical data in the search for
possible drifts of fundamental constants in the early universe. The present
accuracies in laboratory wavelengths of may be considered exact for the purpose of such comparisons.Comment: 13 pages, 6 figures, The Journal of Chemical Physics (2015) accepte
QED effects in molecules: test on rotational quantum states of H
Quantum electrodynamic effects have been systematically tested in the
progression of rotational quantum states in the
vibronic ground state of molecular hydrogen. High-precision Doppler-free
spectroscopy of the (0,0) band
was performed with 0.005 cm accuracy on rotationally-hot H (with
rotational quantum states J up to 16). QED and relativistic contributions to
rotational level energies as high as 0.13 cm are extracted, and are in
perfect agreement with recent calculations of QED and high-order relativistic
effects for the H ground state.Comment: 4 pages, 3 figures, to be published in Physical Review Letter
Constraints on extra dimensions from precision molecular spectroscopy
Accurate investigations of quantum level energies in molecular systems are
shown to provide a test ground to constrain the size of compactified extra
dimensions. This is made possible by the recent progress in precision metrology
with ultrastable lasers on energy levels in neutral molecular hydrogen (H,
HD and D) and the molecular hydrogen ions (H, HD and D).
Comparisons between experiment and quantum electrodynamics calculations for
these molecular systems can be interpreted in terms of probing large extra
dimensions, under which conditions gravity will become much stronger. Molecules
are a probe of space-time geometry at typical distances where chemical bonds
are effective, i.e. at length scales of an \AA. Constraints on compactification
radii for extra dimensions are derived within the Arkani-Hamed-Dimopoulos-Dvali
framework, while constraints for curvature or brane separation are derived
within the Randall-Sundrum framework. Based on the molecular spectroscopy of
D molecules and HD ions, the compactification size for seven extra
dimensions (in connection to M-theory defined in 11 dimensions) of equal size
is shown to be limited to m. While limits on compactification
sizes of extra dimensions based on other branches of physics are compared, the
prospect of further tightening constraints from the molecular method is
discussed
CARS spectroscopy of the () band in
Molecular hydrogen is a benchmark system for bound state quantum calculation
and tests of quantum electrodynamical effects. While spectroscopic measurements
on the stable species have progressively improved over the years, high
resolution studies on the radioactive isotopologues , and
have been limited. Here we present an accurate determination of
transition energies in the fundamental vibrational
band of the ground electronic state, by means of high resolution Coherent
Anti-Stokes Raman Spectroscopy. With the present experimental uncertainty of
, which is a fivefold improvement over previous
measurements, agreement with the latest theoretical calculations is
demonstrated.Comment: 9 pages, 3 figure
Study of the Born-Oppenheimer Approximation for Mass-Scaling of Cold Collision Properties
Asymptotic levels of the A state of the two isotopomers
and up to the dissociation limit
are investigated with a Doppler-free high resolution laser-spectroscopic
experiment in a molecular beam. The observed level structure can be reproduced
correctly only if a mass dependent correction term is introduced for the
interaction potential. The applied relative correction in the depth of the
potential is , which is in the order of magnitude expected for
corrections of the Born-Oppenheimer approximation. A similar change in ground
state potentials might lead to significant changes of mass-scaled properties
describing cold collisions like the s-wave scattering length.Comment: 8 pages, 6 figure
The BX electronic origin band of CH
The rotationally resolved spectrum of the BX electronic origin
band transition of CH is presented. The spectrum is recorded using
cavity ring-down spectroscopy in combination with supersonic plasma jets by
discharging a CH/He/Ar gas mixture. A detailed analysis of more
than a hundred fully-resolved transitions allows for an accurate determination
of the spectroscopic parameters for both the ground and electronically excited
state of CH.Comment: 4 pages, 1 figure, 2 table
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