The transition wave numbers from selected rovibrational levels of the EF (1)Sigma(g) (+)(v=0) state to selected np Rydberg states of ortho- and para-D(2) located below the adiabatic ionization ...threshold have been measured at a precision better than 10(-3) cm(-1). Adding these wave numbers to the previously determined transition wave numbers from the X (1)Sigma(g) (+)(v=0, N=0,1) states to the EF (1)Sigma(g) (+)(v=0, N=0,1) states of D(2) and to the binding energies of the Rydberg states calculated by multichannel quantum defect theory, the ionization energies of ortho- and para-D(2) are determined to be 124 745.394 07(58) cm(-1) and 124 715.003 77(75) cm(-1), respectively. After re-evaluation of the dissociation energy of D(2) (+) and using the known ionization energy of D, the dissociation energy of D(2) is determined to be 36 748.362 86(68) cm(-1). This result is more precise than previous experimental results by more than one order of magnitude and is in excellent agreement with the most recent theoretical value 36 748.3633(9) cm(-1) K. Piszczatowski, G. Łach, M. Przybytek et al., J. Chem. Theory Comput. 5, 3039 (2009). The ortho-para separation of D(2), i.e., the energy difference between the N=0 and N=1 rotational levels of the X (1)Sigma(g) (+)(v=0) ground state, has been determined to be 59.781 30(95) cm(-1).
Crisis and catharsis in atomic physics Ubachs, Wim
Science (American Association for the Advancement of Science),
11/2020, Letnik:
370, Številka:
6520
Journal Article
The status of searches for possible variation in the constants of nature from astronomical observation of molecules is reviewed, focusing on the dimensionless constant representing the ...proton-electron mass ratio
μ
=
m
p
/
m
e
. The optical detection of H
2
and CO molecules with large ground-based telescopes (as the ESO-VLT and the Keck telescopes), as well as the detection of H
2
with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope is discussed in the context of varying constants, and in connection to different theoretical scenarios. Radio astronomy provides an alternative search strategy bearing the advantage that molecules as NH
3
(ammonia) and CH
3
OH (methanol) can be used, which are much more sensitive to a varying
μ
than diatomic molecules. Current constraints are
|
Δ
μ
/
μ
|
<
5
×
10
−
6
for redshift
z
=
2.0
–
4.2
, corresponding to look-back times of 10–12.5 Gyrs, and
|
Δ
μ
/
μ
|
<
1.5
×
10
−
7
for
z
=
0.88
, corresponding to half the age of the Universe (both at
3
σ
statistical significance). Existing bottlenecks and prospects for future improvement with novel instrumentation are discussed.
Molecular hydrogen transitions in quasar spectra can be used to constrain variation in the proton-to-electron mass ratio, μ≡ m
p/m
e, at high redshifts (z ≳ 2). We present here an analysis of a new ...spectrum of the quasar Q0528−250, obtained on Very Large Telescope (VLT)/Ultraviolet and Visual Echelle Spectrograph (UVES), and analyse the well-known H2 absorber at z = 2.811 in this spectrum. For the first time we detect deuterated molecular hydrogen (HD) in this system with a column density of log10(N/cm−2) = 13.27 ± 0.07; HD is sensitive to variation in μ, and so we include it in our analysis. Using 76 H2 and seven HD transitions we constrain variation in μ from the current laboratory value to be Δμ/μ= (0.3 ± 3.2stat± 1.9sys) × 10−6, which is consistent with no cosmological variation in μ, as well as with previous results from other H2/HD absorbers. The main sources of systematic uncertainty relate to accurate wavelength calibration of the spectra and the re-dispersion of multiple telescope exposures on to the one pixel grid.
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