• M N Dixit

Articles written in Proceedings – Section A

• 2Σ→X2Π, band system in PO molecule

The new ultra-violet bands of PO lying in the region 2300–3000 Å and degraded to the red, have been excited in a microwave (2450 mc./s.) discharge and photographed in the second and third orders of 3·4 m. and 6·6 m. grating spectrographs. Vibrational analysis of the R1 and Q2 heads shows that they can be expressed by the relation$$v_h = \left. \matrix{ 43852 \cdot 43 \hfill \cr 628 \cdot 60 \hfill \cr} \right\}\matrix{ { + 826 \cdot 37 (v' + \raise.5ex\hbox{\scriptstyle 1}\kern-.1em/ \kern-.15em\lower.25ex\hbox{\scriptstyle 2} ) - 6 \cdot 96 (v' + \raise.5ex\hbox{\scriptstyle 1}\kern-.1em/ \kern-.15em\lower.25ex\hbox{\scriptstyle 2} )^2 } \cr { - \left\{ {1233 \cdot 38 (v'' + \raise.5ex\hbox{\scriptstyle 1}\kern-.1em/ \kern-.15em\lower.25ex\hbox{\scriptstyle 2} ) - 6 \cdot 56 (v'' + \raise.5ex\hbox{\scriptstyle 1}\kern-.1em/ \kern-.15em\lower.25ex\hbox{\scriptstyle 2} )^2 } \right\}.} \cr }$$. Rotational analysis of the 0–2 and 0–3 bands shows that they arise out of a2Σ−X2Π transition.

The vibrational and rotational constants are

(a)2Σ (initial)state\eqalign{ & w_e ^\prime = 826 \cdot 37 cm.^{ - 1} w_e ^\prime x_e ^\prime = 6 \cdot 96 cm.^{ - 1} \cr & B_0 ^\prime = 0 \cdot 637_8 cm.^{ - 1} r_0 ^\prime = 1 \cdot 582_7 {\rm{{\AA}}} \cr}

(b)X2Π (final)state\eqalign{ & w_e ^{\prime \prime } = 1233 \cdot 38 cm.^{ - 1} w_e ^{\prime \prime } x_e ^{\prime \prime } = 6 \cdot 56 cm.^{ - 1} \cr & B_2 ^{\prime \prime } = 0 \cdot 719_8 a = 0 \cdot 005_2 cm.^{ - 1} \cr}

Coupling constant A2=224·22 cm.−1

• Rotational analysis of some bands of C1Σu+-X1Σg+ system of P2 molecule involving lowν′,ν″ values

Ten ultraviolet bands of the C1Σu+-X1Σg+ system of P2 involving lowv′ andv″ values have been photographed at dispersion of 0·38 and 0·56 Å/mm. and analysed for their rotational structure. While four of these bands were analysed earlier, six of them,viz., 0–10, 1–12, 2–7, 2–14, 4–8 and 6–9 have been analysed for the first time during the present studies. The rotational constants, BvS with lowv″ quantum numbers are obtained from which value of Bθ has been derived. The value of Bθ is found to be in agreement with the value obtained by Douglas and Rao from their study of A1Πg-X1Σg+ bands of P2.

Earlier findings on the perturbation ofν′=2 level of the C1Σu+ state have been confirmed from the analysis of the 2–7, 2–14 and 2–15 bands. Theν00 values of the bands show large deviations from the expected values.

• Isotope shift studies of the ultra-violet and visible bands of P16O and P18O

The spectra of P16O and P18O were excited in sealed discharge tubes containing neon (2–3 mm. pressure), oxygen gas enriched to 65 per cent. of18O and trace amounts of phosphorus vapour and photographed on a 3 m. grating spectrograph at a dispersion of 2·5 Å/mm. Isotope shift studies in theβ-bands confirmed the earlier vibrational scheme of Curryet al. and showed conclusively that the red as well as the violet degraded bands belonged to the sameβ-system. The present studies of isotope shifts also confirmed the vibrational assignments of the extensive ultraviolet bands involving the2Σ−X2Π transition and theγ-bands (A2Σ+−X2Π). In the case of the visible bands, they provided evidence for the first time that the bands at 5585 Å, 5962 Å and 6385 Å belonged to one system and involved 0–0, 0–1 and 0–2 transitions respectively.

• Rotational analysis of the1Π-X1Σ system of AsN

The1Π-X1Σ bands of AsN were excited by means of radio-frequency discharge through nitrogen and helium and traces of arsenic. The 0-0 band (2784.25 Å) and the 0-1 band (2868.74 Å) were photographed in the third order of a 6.6 meter concave grating spectrograph at a dispersion of 0.38 Å/mm. and analysed for their rotational structure. Perturbations observed in the1Π state were studied in detail.

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