Rotational Term Values Research Articles

High-resolution FT-VIS emission spectroscopy of the [formula omitted] system of AlH

An extensive high-resolution visible wavelength emission spectrum of AlH, that covers eight bands of the A1Π−X1Σ+ system, has been observed with a Fourier-transform spectrometer for the first time. The 0−0,1,2 and 1−0,1,2,3,4 bands were recorded with an instrumental resolution of 0.03 cm−1. The best signal-to-noise ratio of 9000:1 was obtained for the strongest 0−0 band. In total, 259 ro-vibronic frequencies were measured with an absolute accuracy of about 0.0020 cm−1. The experimental data were fitted using the PGOPHER program written by Western (2017). Molecular constants were derived for the X1Σ+, ν=0−4 and A1Π, ν=0,1 levels. Also derived were rotational term values for the A1Π, ν=0,1 levels. The current data were combined with the previous ground state results of White et al. (1993) using the instruction called the constraints on parameters within PGOPHER. The Dunham parameters (Ykl) for the A1Π state of AlH were determined for the first time. A very small shifts of the A1Π, ν=0,J=17 and ν=1,J=5 levels have been observed and identified as result of the possible interaction between A1Π and 3Σ+ states.

Deperturbation analysis of the A1Π(v = 2) level in the 12C18O isotopologue

The rotational structure of the A1Π(v = 2) level of 12C18O is re-examined using high-accuracy experimental data comprised of 541 molecular lines obtained by two complementary Fourier-transform techniques. The absorption spectrum of the A1Π – X1Σ+(2, 0) band, in the range 66,500 - 67,650 cm–1, was recorded by the vacuum-ultraviolet FT spectrometer at the DESIRS beamline of the SOLEIL synchrotron. Visible emission spectra of the B1Σ+ – A1Π(0, 2) and C1Σ+ – A1Π(0, 2) bands in the range 19,200 - 20,000 and 24,300 - 24,800 cm–1 were obtained with a Bruker IFS-125HR spectrometer at the University of Rzeszów. The absolute accuracy of line frequencies are 0.01 and 0.005 - 0.01 cm−1, respectively. Results from the B1Σ+ – X1Σ+(0, 0) and C1Σ+ – X1Σ+(0, 0) absorption bands of 12C18O were added to the experimental data set. A deperturbation analysis of A1Π(v = 2) is performed with an effective Hamiltonian and a term-value fitting approach. Accurate molecular constants for A1Π(v = 2) and the e3Σ–(v = 4), d3Δ(v = 7), aʹ3Σ+(v = 12) and I1Σ–(v = 3) perturbing levels were determined. Perturbation parameters of the spin-orbit A1Π(v = 2) ~ [e3Σ–(v = 4), d3Δ(v = 7), aʹ3Σ+(v = 12)] and rotation-electronic (L-uncoupling) A1Π(v = 2) ~ [I1Σ–(v = 3, 4), D1Δ(v = 3)] interactions, were obtained. A significant, indirect influence of the a3Π state on the A1Π state was detected in 12C18O and has therefore been included in the final fit by taking into account the simultaneous a3Π(v = 13) ~ [e3Σ–(v = 4), d3Δ(v = 7), aʹ3Σ+(v = 12)] ~ A1Π(v = 2) spin-orbit/spin-electronic/L-uncoupling and spin-orbit interactions as well as the a3Π(v = 13) ~ [D1Δ(v = 3), I1Σ–(v = 3)] ~ A1Π(v = 2) spin-orbit and L-uncoupling interactions. This work results in determination of 110 rotational term-values for the A1Π(v = 2) state and its perturbers.

Anomalous Intensities in the 2+1 REMPI Spectrum of the E 1Π-X 1Σ+ Transition of CO.

We report on one-color experiments near 214 nm involving the photodissociation of jet-cooled OCS to produce high rotational states (40 < J < 80) of CO (X 1Σ+, v = 0, 1) which were then ionized by 2+1 resonance-enhanced multiphoton ionization via the E 1Π state. The nominally forbidden Q-branch of the two-photon E 1Π-X 1Σ+ transition is observed with intensity comparable to the allowed R-branch. The bright character of the high- J Q-branch lines can be described quantitatively as intensity borrowing due to mixing of the E 1Π and C 1Σ+ states, using J-dependent mixing coefficients extrapolated from the observed Λ-doubling in the lower rotational levels of the E state. In addition to the significant enhancement of Q-branch intensities above the values predicted by conventional two-photon line strengths for a 1Π-1Σ+ transition, the high- J lines of the R- and P-branches appear to be suppressed in intensity by approximately a factor of 3 compared to the unperturbed low- J line strengths, most likely due to perturbations associated with a 1Σ- state. The E-state rotational term values for J < 80, v = 0 derived from the present spectra agree within our measurement and calibration uncertainties with the extrapolations based on the molecular constants previously derived from rotational levels with J < 50. The E-X transition is attractive for future application to photodissociation dynamics and rotational polarization measurements of CO photofragments, with convenient access to state-selective probing on multiple rotational branches, which exhibit different sensitivity to fragment alignment.

Fourier transform emission spectroscopy and ab initio calculations on the visible spectrum of AlD[formula omitted

The spectrum of the AlD+ isotopologue has been investigated at high resolution in the 27,000−29,000 cm−1 region using a Fourier transform emission spectroscopy technique. The AlD+ molecules were produced within a water-cooled aluminum hollow-cathode lamp in the presence of 1.5 Torr of Ne and 0.8 Torr of ND3. The (0, 0) and (1, 1) bands belonging to the A2Π−X2Σ+system were recorded with an instrumental resolution of 0.03 cm−1. In total, almost 500 rotational frequencies were measured with an absolute accuracy of about 0.005 cm−1. It improved the experimental accuracy of the determined frequencies by the factor 10 compared to the previous work [J Phys B: Mol Phys 1984;17:L861-L866]. The rotational analysis has shown irregularities in the Λ− doubling splitting of the A2Π v=0,1. Consequently, the A2Π state has been represented by the rotational term values, while the regular X2Σ+ state by the molecular constants. The causes of the irregularities were identified in the interaction between the A2Π and the B2Σ+ states, which lies about 3720 cm−1 above. Supporting ab initio quantum chemical calculations, including spin-orbit effects, reproduce the observed spectroscopic constants including the small energy splittings due to spin-rotation interactions (for 2Σ+ states) and Λ−doubling.

High-resolution photoelectron spectroscopy and calculations of the highest bound levels of below the first dissociation threshold

Pulsed-field ionization zero-kinetic-energy photoelectron spectra of D2 have been recorded from the intermediate state to determine the positions of bound rovibronic levels of located within 1400 cm−1 of the D+ + D(1s) dissociation threshold. The ion-pair character of the intermediate state resulted in large changes of the rotational quantum number upon photoionization, which enabled the observation of levels of with rotational quantum number as high as 10. The experimental data cover a range of levels within which the usual hierarchy of timescales of the electronic, vibrational and rotational motions is inverted. The term values of these levels with respect to the X rovibronic ground state of D2 and the energy intervals of the ionic states, measured with an accuracy of typically 0.11 cm−1 and 0.02 cm−1, respectively, are compared with positions calculated ab initio at various degrees of approximation, starting from the Born–Oppenheimer approximation and successively including adiabatic, nonadiabatic, relativistic and radiative corrections. The comparison shows that the accuracy of the photoelectron-spectroscopic measurement is sufficient to reveal the effects of the adiabatic, nonadiabatic, relativistic and radiative corrections on the absolute term values. Comparing our calculations, which rely on an approximate evaluation of the nonadiabatic corrections based on effective R-dependent reduced masses, with the theoretical results for by Moss (1993 J. Chem. Soc. Faraday Trans. 89 3851) and for by Wolniewicz and Orlikowski (1991 Mol. Phys. 74 103) enables the quantification of the errors introduced by our approximative treatment of the nonadiabatic corrections. Improved rotational term values of the level were also derived.

Vibrationally and rotationally nonadiabatic calculations onH3+using coordinate-dependent vibrational and rotational masses

Using the core-mass approach, we have generated a vibrational-mass surface for the triatomic ${\mathrm{H}}_{3}{}^{+}$. The coordinate-dependent masses account for the off-resonance nonadiabatic coupling and permit a very accurate determination of the rovibrational states using a single potential energy surface. The new, high-precision measurements of 12 rovibrational transitions in the ${\ensuremath{\nu}}_{2}$ bending fundamental of ${\mathrm{H}}_{3}{}^{+}$ by Wu et al. [Phys. Rev. A 88, 032507 (2013)] are used to scale this surface empirically and to derive state-dependent vibrational and rotational masses that reproduce the experimental transition energies to ${10}^{\ensuremath{-}3}\phantom{\rule{0.28em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$. Rotational term values for $J\ensuremath{\le}10$ are presented for the two lowest vibrational states and equivalent transitions in D${}_{3}{}^{+}$ considered.

Cavity Ringdown Spectroscopy of PH2 Radical in 465–555 nm

Absorption spectra of jet-cooled PH2 radicals were recorded in the wavelength range of 465–555 nm using cavity ringdown spectroscopy. The PH2 radicals were produced in a supersonic jet by pulsed direct current discharge of a mixture of PH3 and SF6 in argon. Seven vibronic bands with fine rotational structures have been observed and assigned as 000, 2n0, and 2n1 (n = 1–3) bands of the Ã2A1−X̃2B1 electronic transition. Rotational assignments and rotational term values for each band were re-identified, and the molecular parameters including rotational constants, centrifugal distortion constants, and spin-rotation interaction constants were also improved with reasonably high precision. In addition, large perturbations observed in each quantum number of total angular momentum of the a axis level of the excited vibronic states were briefly discussed.

光腔衰荡光谱技术研究AsH2自由基:&amp;nbsp;&amp;lt;italic&amp;gt;&amp;Atilde;&amp;lt;/italic&amp;gt;&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;&amp;lt;italic&amp;gt;A&amp;lt;/italic&amp;gt;&amp;lt;sub&amp;gt;1&amp;lt;/sub&amp;gt;(000)&amp;minus;X&amp;lt;sup&amp;gt;~2&amp;lt;/sup&amp;gt;&amp;lt;italic&amp;gt;B&amp;lt;/italic&amp;gt;&amp;lt;sub&amp;gt;1&amp;lt;/sub&amp;gt;(000)

The absorption spectra of AsH2 radical were recorded in 19870―20250 cm−1 by cavity ringdown spectroscopy. The AsH2 radicals were produced by pulsed DC discharge of a gas mixture of AsH3 in argon. Based on the previous studies, the obtained spectra can be assigned as the vibronic transition: A 2 A 1 (000)– X 2 B 1(000). Rotational assignments and least square fittings for about 777 rotational lines with Ka ´≤5 and N ´≤10 were carried out, and the rotational term values and the molecular parameters were also determined with reasonably high precision. The perturbations observed for the upper state were briefly analyzed and discussed.

Absorption spectra of AsH 2 radical in 435–510 nm by cavity ringdown spectroscopy

The absorption spectra of jet-cooled AsH 2 radicals were recorded in the wavelength range of 435–510 nm by cavity ringdown spectroscopy. The AsH 2 radicals were produced by pulsed DC discharge in a molecular beam of a mixture of AsH 3, SF 6, and argon. Seven vibronic bands with fine rotational structures have been identified and assigned as the 0 0 0 , 2 0 n , and 2 1 n ( n = 1–3) bands of the A ∼ 2 A 1 – X ∼ 2 B 1 electronic transition. Based on the previous studies of AsH 2 radical, rotational assignments and rotational term values for each band were obtained, and the molecular parameters including vibrational constants, rotational constants, centrifugal distortion constants, and spin–rotation interaction constants were also determined.

High repetition rate cavity ringdown spectroscopy of vibrational overtones of H 13C 13CH at around 12 200 cm −1

This article describes the measurement and rotational analysis of several overtone vibrational bands of H 13C 13CH in the region between 12 100 cm −1 and 12 265 cm −1 using cavity ringdown spectroscopy. The recorded spectra contain three perpendicular bands and one parallel band. We present rotational parameters and vibrational term values for seven different vibrational states. In the experimental technique employed, the laser source is frequency stabilised to a transmission maximum of a high-finesse ringdown cavity. After each exponential decay, the laser re-acquires the lock and maintains it until the next ringdown is commenced. Some improvements have been made to the initial version of the experimental setup and these are discussed.

Ro-Vibrational States of Triplet H2D+

We present rotational term values for J < or = 3 of the vibrational states with up to twofold excitation of H2D+ in the lowest electronic triplet state (a3sigma(u)+). The calculations were performed using the method of hyperspherical harmonics and our recent accurate double many-body expansion potential energy surface.

New S1 state vibrational and T3, 2, 1 spin–rotational assignments in the vicinity of the acetylene [formula omitted] band

Pulsed supersonic jet spectra of acetylene have been recorded in the vicinity of the A ˜ 1 A u – X ˜ 1 Σ g + V 0 3 K 0 1 band in two mutually exclusive detection channels: ultraviolet laser-induced fluorescence (UV-LIF) and surface electron ejection by laser excited metastables (SEELEM). No eigenstate of the upper state(s) can appear via transitions in both UV-LIF and SEELEM channels. The UV-LIF channel is blind to transitions into eigenstates that have lifetimes longer than a few microseconds, while the SEELEM channel is exclusively sensitive to transitions into electronically excited eigenstates that have lifetimes longer than ∼30 μs. It is observed that intersystem crossing from the à ( S 1) bright state to the dark triplet states is mediated through a single “doorway state” vibrational level of the T 3 electronic state. We have characterized the bright state, the doorway state, and the dark states (singlet as well as triplet) illuminated by the bright state. Rotational transitions that belong to several previously unassigned vibrational-symmetry-allowed but nominally Franck–Condon forbidden S 1 ← S 0 electronic-vibrational bands are detected and assigned in the UV-LIF spectrum. The UV-LIF spectrum reveals that the electronic symmetry of the T 3 state is 3 B u and the K′ value of the observed T 3 ← S 0 vibrational band segment is 1. From the SEELEM spectrum, nine vibrational levels of dark triplet states are observed, spread over only ∼2.42 cm −1. Unique N, K, and e/ f quantum numbers are assigned for all of the observed triplet spin-rovibronic levels. Electronic symmetries for seven of the nine triplet states are determined. Most of the triplet state vibrational levels observed in the SEELEM spectrum belong to the T 1 surface ( 3 B u and 3 B 2) at energy well above the barrier to linearity. Despite the high vibrational state density, the upper levels of all of the assigned spin-rovibronic transitions fall onto surprisingly regular rotational term value plots [ E′ vs. N′ ( N′ + 1)] and the intensities fall onto surprisingly smooth Boltzmann plots. The most remarkable thing about the SEELEM spectrum is its apparent regularity, combined with a vibrational density of states so high that anharmonic and a-type Coriolis coupling among the T 1 and T 2 vibrational levels is essentially complete. The spectroscopically observed density of K-assigned vibrational states is comparable to the calculated symmetry-sorted state density.

Application of a VUV Fourier transform spectrometer and synchrotron radiation source to measurements of. VI. The ε(0,0) band of NO

The ε(0,0) (D 2Σ+–X 2Πr) band of NO has been recorded by using a vacuum ultraviolet Fourier transform spectrometer from Imperial College, London, with synchrotron radiation at the Photon Factory, KEK, Japan, as a continuum light source. Analysis of the ε(0,0) band provides accurate rotational line positions and term values as well as the photoabsorption cross sections. Molecular constants of the v=0 level of the D 2Σ state have been determined as T0=53 291.10±0.10 cm−1, B0=1.991 07±0.000 05 cm−1, and D0=(6.6±0.1)×10−6 cm−1. Accurate rotational line strengths have also been obtained and the sum of the line strengths for all rotational lines is determined as 2.18×10−15 cm2 cm−1. The band oscillator strength of the ε(0,0) band is determined to be (2.47±0.12)×10−3.

Ro-vibrational states of triplet H 3+ ( a3Σ u+): The lowest 19 bands

We have performed extensive calculations of the ro-vibrational states of triplet H 3 +, using the method of hyperspherical harmonics and our recently reported double many-body expansion potential energy surface. The rotational term values of the lowest 19 states are presented here for a total angular momentum of J⩽10.

The application of a vacuum ultraviolet Fourier transform spectrometer and synchrotron radiation source to measurements of: V. The β(11,0) band of NO

The β(11,0) band of NO was measured at high resolution (0.06 cm−1) by the vacuum ultraviolet Fourier transform spectrometer from Imperial College, London, using synchrotron radiation at the Photon Factory, KEK, Japan, as a continuum light source. Such resolution facilitates a line by line analysis of the NO β(11,0) band which yields accurate rotational line positions and term values as well as the photoabsorption cross sections. The molecular constants of the B(11) Πr2 level are found to be T0=55 983.203±0.017 cm−1, A=47.977±0.024, Bv=1.010 77±0.000 37 cm−1, Dv=(6.7±0.8)×10−6 cm−1 and AD=0.0438±0.0035 cm−1. The sum of the line strengths for all rotational transitions of the NO β(11,0) band is determined as 3.04×10−16 cm2 cm−1, corresponding to a band oscillator strength of (3.44±0.21)×10−4.

An optical-optical double resonance study of the d3sσg(1Πg) Rydberg state of O2 using b(1Σg+) as the resonant intermediate state

The v=0 level of the d3sσg(1Πg) Rydberg state of O2 has been excited in a two-color optical-optical double resonance (OODR) multiphoton ionization experiment via b(1Σg+: v=0,J=0–16). Rotational term values are reported for J=1–18. A 1+(1+1′) OODR scheme was used, followed by ionization with one more probe photon and detection in the O2+ channel. There are several power-dependent features of the spectra, notably accidental resonant enhancement of the ionization step with an additional pump photon, which indicate that the b state could be a useful resonant intermediate for accessing both higher gerade and ungerade states of O2.

The application of a vacuum ultraviolet Fourier transform spectrometer and synchrotron radiation source to measurements of: IV. The β(6,0) and γ(3,0) bands of NO

The β(6,0) (B 2Πr–X 2Πr) and γ(3,0) (A 2Σ+–X 2Πr) bands of NO have been recorded using a vacuum ultraviolet Fourier transform spectrometer with synchrotron radiation as light source. The analysis of the β(6,0) and γ(3,0) bands of NO provides accurate rotational line positions and term values. Molecular constants of the v=6 level of the B 2Πr and v=3 level of the A 2Σ+ have been determined. Accurate rotational line strengths have also been obtained. The band oscillator strength of the β(6,0) and γ(3,0) bands are determined to be 0.48×10−4 and 2.69×10−4, respectively.

The Visible and Near Ultraviolet Rotation–Vibration Spectrum of HOD

A Fourier transform spectrum has been recorded of a H2O/D2O vapor mixture in the wavenumber range 16,300 to 22,800 cm−1 using a long path cell. 410 lines of HDO are assigned to the OH stretching overtone bands 5ν3, 6ν3 and 7ν3 plus combination bands. Assignments for the 6ν3 and 7ν3 bands represent the first data for the 006 and 007 states and give band origins of 19,836.88 cm−1 and 22,625.50 cm−1, respectively. Rotational term values for these states are also obtained.

The application of a vacuum ultraviolet Fourier transform spectrometer and synchrotron radiation source to measurements of the III ε(1,0) band of NO

The ε(1,0) band of NO was measured at high resolution (0.06 cm−1) by the vacuum ultraviolet (VUV) Fourier transform spectrometer from Imperial College, London, using synchrotron radiation at the Photon Factory, KEK, Japan, as a continuum light source. Such resolution facilitates a line by line analysis of the NO ε(1,0) band which yields accurate rotational line positions and term values as well as the photoabsorption cross sections. The molecular constants of the D(1) Σ2 level are found to be T0=55 570.582±0.055 cm−1, Bv=1.979 66±0.000 19 cm−1, Dv=(5.8±4.7)×10−5cm−1, γ=−0.127±0.008 cm−1 and γD=−(1.03±0.04)×10−3 cm−1. The sum of the line strengths for all rotational transitions of the NO ε(1,0) band is determined as 2.55×10−15 cm2 cm−1, corresponding to a band oscillator strength of 0.002 88±0.000 17.

Two-electron relativistic corrections to the potential energy surface and vibration–rotation levels of water

Two-electron relativistic corrections to the ground-state electronic energy of water are determined as a function of geometry at over 300 points. The corrections include the two-electron Darwin term (D2) of the Coulomb–Pauli Hamiltonian, obtained at the cc-pVQZ CCSD(T) level of theory, as well as the Gaunt and Breit corrections, calculated perturbationally using four-component fully variational Dirac–Hartree–Fock (DHF) wavefunctions and two different basis sets. Based on the calculated energy points, fitted relativistic correction surfaces are constructed. These surfaces are used with a high-accuracy ab initio nonrelativistic Born–Oppenheimer (BO) potential energy hypersurface to calculate vibrational band origins and rotational term values for H 2 16 O . The calculations suggest that these two-electron relativistic corrections, which go beyond the usual kinetic relativistic effects and which have so far been neglected in rovibrational calculations on light many-electron molecular systems, have a substantial influence on the rotation–vibration levels of water. The three effects considered have markedly different characteristics for the stretching and bending levels, which often leads to fortuitous cancellation of errors. The effect of the Breit interaction on the rovibrational levels is intermediate between the effect of the kinetic relativistic correction and that of the one-electron Lamb-shift effect.