Forbidden Transitions in Diatomic Molecules: V. The Rotation–vibration Spectrum of the Hydrogen-Deuteride (Hd) Molecule

Abstract

The 1–0, 2–0, and 3–0 rotation–vibration bands of HD have been observed with a PbS infrared grating spectrometer and the 3–0 and 4–0 bands have been photographed with a 21-ft concave grating spectrograph. From these spectra precise values of the vibrational and rotational constants of HD in its electronic ground state have been determined. The variation of Bv and ΔG with v is similar to that recently established for H2, that is, the values for v = 0 and 1 are markedly above the values corresponding to a linear extrapolation of the subsequent points. This leads to an uncertainty in the ωe and Be values which is much greater than that of the ΔG and Bv values. The (very low) intensity of the rotation–vibration spectrum of HD is in close agreement with that predicted. The decrease of intensity in going from 1–0 to 4–0 is strikingly slow, far slower than in a normal series of fundamental and overtone bands. This also is in qualitative agreement with theoretical expectation for a molecule like HD which does not have a dipole moment in its equilibrium position.

Electric quadrupole and dipole transitions of the first overtone band of HD by CRDS between 1.45 and 1.33μm

“…For instance, our experimental value of the R(8) transition deviates by 0.09 cm À1 from the value calculated with the parameters of Table 2. The only previous derivation of the v = 2 constants of HD was obtained by McKellar [6] on the basis of the positions of seven lines measured by Durie and Herzberg [3]. The corresponding values included in Table 2 agree within the error bars.…”

“…To the best of our knowledge, the only previous observations concerning this band are due to (i) Durie and Herzberg [3] who measured the positions of seven transitions (P(1)-P(3) and R(0)-R(3)), (ii) McKellar [6] who measured the intensities of the P(1), R(0) and R(1) lines and more recently, (iii) Lin et al [16] who reported the centre of the P(5) line with an accuracy better than 0.01 cm À1 . The sensitivity provided by the CRDS technique has allowed us to measure accurately not only the P(1)-P(2) and R(0)-R(8) electric dipole transitions but also the Q(1)-Q(4) and S(0)-S(4) electric quadrupole transitions.…”

“…1 shows an overview of the spectrum. We have included in Table 1, the position values reported in the pioneer work of Durie and Herzberg [3]. To the best of our knowledge, these values are, with the P(5) position of Ref.…”

“…Since then, several experimental works have been devoted to the detection and measurement of HD transitions from the pure rotational spectrum to the (6-0) vibrational band near 520 nm [3][4][5][6][7][8][9][10][11][12][13][14][15][16]. A major contribution is due to Robert McKellar et al who reported position and intensity measurements in a series of contributions published in the 1970s and early 1980s [4][5][6][7][8].…”

VUV-synchrotron absorption studies of N2 and CO at 900K

“…The latter comparison suggests that electric-field induced frequency shifts are less severe than pressure-induced systematic shifts, even after pressure-shift corrections. Durie and Herzberg [84] recorded the weak dipole absorption spectrum of the (1,0), (2,0), (3,0) and (4,0) bands in the ground state of HD. Stoicheff [75] performed Raman spectroscopy on the fundamental band of HD, while Brannon et al [85] measured electric-field induced transitions in the same band.…”