86 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
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
Sub-Doppler frequency metrology in HD for test of fundamental physics
Weak transitions in the (2,0) overtone band of the HD molecule at m were measured in saturated absorption using the technique of
noise-immune cavity-enhanced optical heterodyne molecular spectroscopy. Narrow
Doppler-free lines were interrogated with a spectroscopy laser locked to a
frequency comb laser referenced to an atomic clock to yield transition
frequencies [R(1) = kHz; R(2) =
kHz; R(3) = kHz] at three
orders of magnitude improved accuracy. These benchmark values provide a test of
QED in the smallest neutral molecule, and open up an avenue to resolve the
proton radius puzzle, as well as constrain putative fifth forces and extra
dimensions.Comment: 5 pages, 4 figure
Novel techniques in VUV high-resolution spectroscopy
Novel VUV sources and techniques for VUV spectroscopy are reviewed.
Laser-based VUV sources have been developed via non-linear upconversion of
laser pulses in the nanosecond (ns), the picosecond (ps), and femtosecond (fs)
domain, and are applied in high-resolution gas phase spectroscopic studies.
While the ns and ps pulsed laser sources, at Fourier-transform limited
bandwidths, are used in wavelength scanning spectroscopy, the fs laser source
is used in a two-pulse time delayed mode. In addition a Fourier-transform
spectrometer for high resolution gas-phase spectroscopic studies in the VUV is
described, exhibiting the multiplex advantage to measure many resonances
simultaneously.Comment: 17 Pages, 8 figures, Conference proceedings of the VUV/X-ray 2013 at
Hefei, Chin
UV frequency metrology on CO (a3Pi); isotope effects and sensitivity to a variation of the proton-to-electron mass ratio
UV frequency metrology has been performed on the a3Pi - X1Sigma+ (0,0) band
of various isotopologues of CO using a frequency-quadrupled injection-seeded
narrow-band pulsed Titanium:Sapphire laser referenced to a frequency comb
laser. The band origin is determined with an accuracy of 5 MHz (delta \nu / \nu
= 3 * 10^-9), while the energy differences between rotational levels in the
a3Pi state are determined with an accuracy of 500 kHz. From these measurements,
in combination with previously published radiofrequency and microwave data, a
new set of molecular constants is obtained that describes the level structure
of the a3Pi state of 12C16O and 13C16O with improved accuracy. Transitions in
the different isotopologues are well reproduced by scaling the molecular
constants of 12C16O via the common mass-scaling rules. Only the value of the
band origin could not be scaled, indicative of a breakdown of the
Born-Oppenheimer approximation. Our analysis confirms the extreme sensitivity
of two-photon microwave transitions between nearly-degenerate rotational levels
of different Omega-manifolds for probing a possible variation of the
proton-to-electron mass ratio, \mu=m_p/m_e, on a laboratory time scale
Two-photon Doppler-free ultraviolet laser spectroscopy on sulphur atoms
The P - P transition in the
sulphur atom is investigated in a precision two-photon excitation scheme under
Doppler-free and collision-free circumstances yielding an absolute accuracy of
0.0009 cm, using a narrowband pulsed laser. This verifies and improves
the level separations between amply studied odd parity levels with even parity
levels in S I. An improved value for the P - P ground
state fine structure splitting is determined at (7) cm. A
S - S atomic isotope shift was measured from combining
time-of-flight mass spectrometry with laser spectroscopy.Comment: J. Phys. B: At. Mol. Opt. Phys (2020
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