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# Diatomic Spectral Database, Introduction

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### Introduction

These tables represent the first part of a series of critical reviews on the microwave spectra of molecules. The present review on diatomic molecules is a revision of the "Microwave Spectral Tables, I. Diatomic Molecules" [1].

The original publication in 1974 covered 83 diatomic species, while the present version adds 38 new species and updates the tables for 27 of the original species covered as listed in Table 1. These additions and updates cover the period roughly between 1973 to 1985, although a few later references are also included. Both the new and updated tables follow the general description given in Sections 1, 2, and 3 of the earlier publication, however, several changes have been incorporated in this electronic version. First, a few errors in the 1974 version have been corrected and will be listed below for species not listed in Table 1. Second, the referencing method used previously included numbers in the range of 1 to about 2000, as given by the Favero bibliography [2]. In order to make the referencing method consistent, these were converted to the five-digit format, which starts with the last two digits of the year of publication and then sequential numbers as references are added. This method was used for most of the references in the 1974 publication, as well as for the "Microwave Spectral Tables II. Triatomic Molecules" [J. Phys. Chem. Ref. Data 7, 1445 (1978)], and "Microwave Spectral Tables III. Hydrocarbons" [J. Phys. Chem. Ref. Data 18, 1245 (1989)]. Third, the conversion factor for deriving the internuclear distances, re, from the rotational constant, Be, has been updated using the fundamental constants from P.J. Mohr and B.N. Taylor, J. Phys. Chem. Ref. Data (1999) (see physics.nist.gov/constants) using the following equation:

$$Y_{01} \cong B_{\rm e} ({\rm MHz}) = {\displaystyle \frac{505\,379.006 (51)} {\mu_{\rm r} r_{\rm e}^2 ({\rm u}\, \mbox{Å}^2)}} ~ .$$

[L]

The atomic masses are now taken from G. Audi and A.H. Wapstra, Nucl. Phys. A 575, 409 (1995). All internuclear distances derived here (no reference given) use this conversion factor and masses from the reference above. In Section 3, Equilibrium Internuclear Distances, the old conversion factor of 505 390.98(350) was used and the masses from A.H. Wapstra and N.B. Gove, Nuclear Data Tables 9, 265 (1971). To convert the values to the new conversion factor, divide re by 1.000 011 85. The uncertainty due to the differences in masses in µr is typically 1x10-7 or less.

### Corrections to the 1974 Version

In cases where a complete revision was not warranted, we list the following changes from the original version:

The unit for the atomic mass constant changed from amu to u (1/12 of the mass of 12C), and the unit symbol for the nuclear magneton is µN rather than µn.

For KCl and NaCl the Y03 units changed from Hz to mHz or 10-3 Hz.

For LiCl the value of Y01 (6Li37Cl) = 23 925.383(6) the italic digit (9) changed.

The upper and lower energy state F quantum numbers for 2H16O 2Π3/2 from reference [73009] have been reversed.

For 15N16O Y02 value the decimal point was missing and should read –0.139(5) rather than -139(50).

For SnO the frequencies for 118Sn16O (42 612.85 υ=0;42 354.88 υ=1; and 42 096.20 υ=2) were mislabeled and attributed to the 119Sn species. The value of the reduced mass, µr, for 119Sn16O should read 14.098 394 2 u.

### Table 1. New and updated molecular species.

New Species
ArH+ BCl BaCl BaF
BaS BiBr BiCl BiF
BiI CCl CF CH
CO+ CaBr CaCl CaF
CaO CuBr CuCl CuI
FeO IO MgO NCl
NH NO+ NaH PF
PO SH S2 SeO
SiCl SiF SiN SrCl
SrF SrO

Updated Species
AgI BaO BrCl BrF
BrO CN CO CS
ClF ClO GaBr GaI
GeS GeSe HBr HI
IBr ICl InBr LiH
NO OH O2 RbBr
SF SO SiO

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Created April 24, 2018, Updated June 2, 2021